It's funny you say that about the RE600's because before these E100's the best headphone/IEM I had heard were the Dunu DN-1000's I had right before discovering the E100. Yes, they're incredibly cheap compared to what I owned previously (in some cases like 10x less!) but it's just the liveliness and fun of them had me hooked. Sure I can say this IEM or this headphone did this or that better...for sure...but as a over all package they were a blast.
That's how the E100 is. Yeah it isn't perfect, well scratch that, to me it is. In all honesty the only thing I'd consider them to be outclassed in is the bass. BUT that's only by the JH16Pro FP and that would purely be in the quantity and not quality. While the JH16's had MONSTER bass it was also incredibly sloppy and loose. Other than the JH16's thought the E100's have the best bass and everything I've heard compared to everything I've owned.
As far as frequency response goes I know EXACTLY where you're coming from. A lot of the more popular IEM's out there are things I don't even understand how people can like them. Though, it has to be said that I have owned a lottttt of stuff over the years so I also think I might be a bit bias on this one as my experience far surpasses that of a lot of people, even headphone enthusiasts.
So what are you main runner ups so far other than the RE-600S? I haven't heard them before but I will say I'm not a fan of flat. I like more forward mids and more high sparkle and deep rumble bass.
RE-600S's bass needs to be elevated and the treble too, in order to sound more dynamic and punchy (and closer to being neutral/flat). Take a look at the EQ curve I posted previously in this thread for the RE-600S to see how far it is from neutral/flat.
Most people mistakenly think neutral/flat is boring and lifeless, but that's incorrect. Neutral/flat/accurate means all frequencies are perceived as equal in amplitude/energy when all frequency ranges are compared to each other (such as playing a log sweep test tone, pink noise, or jumping around the different frequencies), and when you get neutral/flat/accurate, the sound is clear, punchy, full, and balanced.
Other than RE-600, the RE-400 might be a better value because it measures so damn similar as the RE-600, but costs less than half of RE-600.
I suspect the Dunu Titan 1 will sound very good too, but I won't know until I get it in my ears a couple of days from now (the seller just shipped it out today).
I'm hoping the 1964 EARS U5 will sound good too, but I'm not optimistic at this point due to past experiences. We'll see.
If Dunu Titan 1 and U5 don't work out, then I guess my final choice will be RE-400, since it's so damn cheap and non-offensive, and can be EQ'd to sound just right. At that price point, even if it breaks after a year or two, I'd just get another one and not feel bad about it. Also, the form factor is so comfortable and tiny--it's a win-win.
If my main source of listening is through IEMs, then I'd choose one of the TOTL IEMs and simply EQ that upper-mids/lower treble peak down to comfortable level, since TOTL IEMs tend to have better drivers with better technology, lower distortion, better transients, etc. But my main source of listening is with full-range speakers (Klein + Hummel O 300Ds and Neumann KH 805 subwoofer, in acoustically treated audio production studio), and even when using headphones, my preference is full-sized headphones, so I'm not going to be as picky about IEMs that I rarely ever listen to anyway (only when I go out, and I rarely go out). As long as it's not offensive sounding and can be EQ'd to sound pretty neutral/accurate, I'm fine with it.
