Often neutral is more a matter of midrange in many cases. A lot of earphones are V shaped to generate bass and treble emphasis for wow factor and because many seem to expect it (youthful tuning). A neutral earphone doesn't specifically throw away bass or treble but simply evens out the presentation, bringing that midrange back into the picture. There is less wow but more balance. The challenge then becomes a matter of if the neutral earphone is too analytical, bland, sterile. These are greater dangers than simply being flat in response.
Now using the Triple.Fi 10 and the DBA-02/Brainwaves B2 you are relatively used to aggressive treble. I'm sure you enjoyed the Triple.Fi 10 with it's excellent breadth of response, thick (for a BA) and powerful bass and still sweet and detailed highs. The Brainwaves probably gave you a new sense of crispness and energy as well as a perception of better balance. However, that lack of low end and even midrange body really does lean out the sound quite a lot. It's a stark contrast to the Triple.Fi 10 on the low end.
Understand that the CK10 is not the same as the B2. They are markedly different sounding earphones. However when we're talking about a significant amount of treble energy, extension, and speed, they tend to be talked about together. The CK10 is more dynamic, better textured, and better balanced. I view the CK10 as superior in most every way including offering a more balanced presentation and fuller low end. The CK10 is incredibly good and the most realistic sounding earphones I've used. I personally was not impressed by the DBA-02 I owned briefly. I felt it was an excellent attempt, but compressed dynamic range and very short decay were serious problems when it came to actually fully reproducing sounds. The CK10 is significantly better and in my eyes is one of the least faulted earphones I've used. It wasn't my personal favorite, but it was one of the most technically correct earphones I've used. I view the CK10 has lightyears better than the DBA-02/Brainwaves B2. I would rather use something like the $99 RE-Zero over the DBA-02 for a more even, natural, and well presented sound.
In terms of overall performance I view products like the Triple.Fi 10, CK10, e-Q5/e-Q7, and quite a number of other top tier earphones as all on the same level, just offering very different sound signatures to suit a wide array of preferences. It's not so much that one is better than another. It's more that they are all good bit geared for a different thing. The inherent challenge then becomes finding the one product that best fits your personal preference. Now you like treble certainly. Enjoying the top end power of the B2 and Triple.Fi 10 sort of require that you do. At the same time you understand a need for more low end body and presence, something you saw in the Triple.Fi 10 but not the B2.
You concern yourself with sound stage, instrument separation, and placement. That's good. It is important not only to make sound cleanly but also to create a fully developed presentation. To do this you focus on two main areas. To convey distance, you need a range of volume. Higher dynamic range as well as good linearity of this range creates that distance. Close is loud and far is quiet. Any dynamic compression will limit the size of the stage space. An inability to portray subtlety well will prevent a good sense of depth. An inability to portray loudness and what I like to call "explosiveness" prevents the ability to portray proximity and intimacy. Step one is to have at least a reasonable dynamic range along with some ability to convey subtle and loud information well.
Part two of this sound stage equation requires information to fill out the space. You need to be able to hear the smaller echos and noises in the background to generate a mental picture of the room. Close your eyes at home and say something. Note how you perceive the room space. You don't hear the space with your voice. You hear the space from the echos and reverberations after. They are quiet and complex, noisy, and random. An earphone needs to be able to portray these background noises in order to really flesh out the sound and make it "real" in your mind. Too little and it can sound a bit hollow, ghostly, or non-existent. So what's needed to get these sounds? First, you need time and for an earphone this means decay of a reasonable length. If the decay is super short it offers too little time to allow these details to show through even if the earphone is very fast. This plagues some excellent earphones like the SE530 and RE262. Now we not only need decay but we also need information there. If an earphone is too smoothed or sluggish, we lose some of those smaller details. Thick, sloppy earphones may have a lot of presence and sound full and enveloping but can't provide the information to materialize the stage space. What we need is detail, so we need an earphone of good decay time but also with moderate speed and texturing. We want those micro details to show through and be heard. Good decay and good texture will give us this. A slow earphone will lack texture and be too smoothed and with low detail. A fast earphone (with decay) will be textured with a good amount of that small, background detail. To an extreme, we can even get a very articulate and almost chiseled level of detail, very high and very exact, although not many go this far.
Separation is pretty easy to do without high dynamics or much decay. Separation in itself is about cleanliness of note, enough speed and control to keep things from being muddled together. Something like the B2 is good about this because it's rather quick. The Triple.Fi 10 is a bit thicker and smoother in note (very thick for a BA) and does start to blur stuff just slightly.
In the end, the goal is to try and get a reasonable amount of all the qualities. We want to have the dynamic breadth. We want to have a reasonable amount of decay time in the note. We want enough speed to show detail and texture during this decay time. Good speed and dynamics often also make a relatively well articulated sound as long as the sound isn't too heavily controlled (ex. dynamic driver with a lot of damping). We just want a good mix of everything, and as long as we have everything, we get a good, comprehensive sound that caries all the information we need.
When talking about the mix, I like products such as the e-Q7 because it offers that good mix of everything in a balance that works well. It's why I've stuck onto it and why it is one of my favorites. This isn't to say there aren't good mixes in other products. The CK10 does very well. The e-Q5 does very well. Most any Westone does very well. Klipsch's Custom 3 does very well. The FX700 does very well. The list is long, although they do all vary somewhat in mix and amount of each trait. Some have longer decay than others, some more detail, some more dynamic breadth. The end result varies some. In the end, most are good choices, but the exact fit is different. Without you having a large experience with many earphones and myself not knowing exactly what you like, it's hard for me to point you to one specific product and say "Yep, this one best fits you." I can guess and be close, but maybe I'm a touch off and the other option actually fit you better. If I were to suggest blindly, the Ortofons certainly are a good start. The e-Q5 is a little brighter, crisper, and upbeat. the e-Q7 is a little more laid back, thicker, and bodied. I favor the e-Q7 personally, but they're both a slight twist on the same good thing. The GR07 may also be a great choice. It's less dynamic however, but the level of detail is high, and it offers an excellent amount of decay on the low end. It's clean and super transparent. The limited dynamic breadth due to what I think is a somewhat weak motor for the driver (break in and amping doesn't help) does bug me personally. However, the balance, breadth, and monitor quality presentation does make it a serious contender anyways. it pretty much only has the one gripe, and that's it. As I already said before, the CK10 is one of the most technically correct earphones I've used, very little to complain about and extremely realistic sounding. It's remarkably good in almost every way short the narrow 10kHz response spike that tend to make it just little hot and spitty with certain music. Because you don't actually seek a highly balanced sound and don't mind a V shaped response, I would certainly suggest the Westone 3 or 4 earphones if your budget allows. These are outstanding products that are remarkably good. While I did mention the FX700 above, I will shy you away from it if treble and top end air and sparkle is one of your goals. It simply doesn't have it. The top end is laid back and rolls off. It's extremely good otherwise and fits a lot of what you seek. I would just instead point you towards the Westones as something similar in performance but with more top end.
Yes, there are lots of choices. The IEM market has exploded over the last several years, so you have the joy of weeding through many great candidates. The hard part is not finding one that's good. The hard part is finding one that you will actually like that fits your personal preferences almost exactly. That is the greatest challenge.