NE-7M may work well for you. It's a cleaner, more articulate sound then the Vibe but still full bodied and warm sounding. They isolate better then the Vibe. They're also insanely easy to power, very high sensitivie, and they'll get quite loud without breaking up, the benefit of efficiently using power.
The lower treble is accentuated, so you'll get better high frequency detail then the Vibe. They still roll off up top like the Vibe though, so they're not sparkly or ultra crisp sounding. If you're looking for a full bodied sound, they're a good pick. If you're looking for high detail, clarity, and a more analytical presentation, then they aren't really capable.
I'm curious if something like the Etymotic ER6i or similar may work too, especially if you're looking for a lot of isolation and high detail. Street price is within your budget. They heavily isolate and are geared for mp3 players. I haven't personally listened to a set, but there are plenty of reviews around.
The Altec Lansing IM716 is a similar option and a very well regarded IEM option. It has a bass mode that apparently keeps it from being overly bass light and gives it some warmth, again a IEM I haven't listened to. The sound is supposed to be similar to the ER6i but with a little more bass. There's also a resistor mod that can be done to change the sound (people like it better) and improve mp3 player use (better sensitivity). The IM716 is also quite cheap at
Newegg.com - Computer Parts, PC Components, Laptop Computers, Digital Cameras and more!
I've used the higher level Denon C700, but haven't used their mid level product.
If the design is similar, expect relatively low max output (like half of most other IEMs) before they run out of excursion and distort in bass frequencies, and expect pretty low isolation, worse then the Vibe. The Denon products seem geared for quiet, critical listening rather then on the go jammin'.
I'm kind of a big fan of the Vibe cause I do enjoy that warm, velvety sound, but I agree top end is mild because of the roll off around 10kHz and it is a sloppy sound. Amping does clean up the bass though, but it's not a world of difference. For someone who wants precise articulation of note, the Vibe simply doesn't cut it.
It just seems you are at the point where you really do want something more analytical. If you don't need heavy bass, the Etymotic and Altec Lansing options may be a good fit. They'll give you the precision and detail and upper end response lacking from the Vibe. The only common complaint is bass but the ER6i and IM716 have their bass accentuated.