New job and soon new IEMs, need some advice

I just found out today I got a job I was really hoping for. (Woot!) One of the benefits of said job is I can finally look into upgrading my audio gear. I'm going to do it slowly and by necessity first. I have a good set of cans for at home on my desktop, but my IEMs need improving. I currently have a set of UE700's as well as a Denon D2000 for home use (it's time will come). No DAC/AMP as of yet but that's also on the list.

Right now, I'm just looking to replace the UE700's. The budget I'm looking in is the $400-$600 range of custom IEMs. I thought about jumping to $700 but I have a feeling that for my needs it'll be overkill.

Use case is to and from work (sourced through my iPhone which is mostly ALAC or AAC 256+ audio) as well as at work where it will eventually be paired with some portable DAC/AMP.

Given that the headphones I've mentioned are the ones I know the most, I'll speak directly from them. The UE700's are a bit weaker on bass than I'd like and can sound a bit hollow. The Denon's have great bass but can sound a bit flat to my ears, especially in the high-mids.

One other thing is the reason I'm considering custom IEMs (my first of such) is because I'll likely be wearing them for hours at a time as well as having to regularly take them out. I find universal IEMs with Comply Foam tips can be a bit annoying because you have to squish the tip, push it in, and hold it for half a second so it's in properly. Customs just seem like they'd be simpler in that regard, if only just.

So things on my radar are the Unique Melody Aero and Merlin, UE5, UE7, 1964 Triple and Quad, JH5. I thought about the JH7 but it's just too much and for what I'm talking I don't think it'd be right for me.

I have heard the UM's have great build quality but can be weaker on the bass. I have a feeling UE suffers from the same issue. However, I don't really know much about the 1964 or JH Audio headphones in terms of sound signature.

What do you guys think? Which ones would make the best post-Christmas gift to myself? I'm looking to buy sometime in February but I'm a big fan of figuring this sort of stuff out beforehand.

So... No one has any advice?

@Zarim: I did a quick look around and didn't see any for sale. I'll keep my eyes out, though. A used set of JH13's in good condition would be well worth the money even if I had to pay to have them re-shelled. As it is, do you happen to know how much that whole process would cost, aside from getting castings of my ears and the like.

@alv4426: I hadn't heard of those, I'll definitely have a look. Taking a quick browse they look fantastic.

@kckc: Yeah, build quality is something I keep hearing is wonderful in UM IEMs. My only concern is how far away they are and how that adds to costs, getting serviced, ect.

As a sort of general, I've always been a bit wary of IEMs that have 3+ drivers for the same price of others that only have 2. My fear is how can these be as high of quality components if a similar IEM from JH Audio or Ultimate Ears costs twice that? Is part of it just brand hype or is there really something to it?

Just a status update. I've been asking around, contacting companies, getting opinions... And saving monies. The result? First week of February I'll be putting in an order for some Heir Audio 4.A CIEMs.

But first, I need to find an audiologist in San Francisco. Any recommendations would be appreciated.