Amongst the high end IEMs:
The U10-Pro are probably one of the most popular - how can you not like the name "Ultimate Ears" when it comes to audio equipment. Some consider these the natural progression for Etymotic users.
Sensaphonics ProPhonic 2X-Soft - Also a large number of followers, and a direct competitor to the UE-10 Pro, even though it uses dual drivers rather than triple. Supposed to be bassier.
Westone ES-3 I have the feeling they are not as often mentioned as the other two (strange considering the UM2 is fairly popular). But it is also a direct competitor to the above two.
Well, since I've never used any of the above, I am not sure how well they sound on
MP3. But they are clearly designed for portable use, so I guess a good encode should sound fine. But I reckon this is one case where lossless might be beneficial. Some reviewers on head-fi seem to think so anyway.
That said. I -think- that if money was an issue (and it is) I would much rather use that money to buy two mid/high end open headphones for home use, and something slightly less fancy "on the go". I suspect a high end open headphones can be every bit as competitive to the UE-10 Pro (speculation on my part).
If the words "what the... people spend that much on just IEMs?", then I'd argue that at least those things are much longer term investment then.. say, X1900 Crossfire