Future Sonics Atrio M5s or M8s -- for (well) under $200. Rich, deep bass, but not bloated. Well worth the extra effort to seek them out and get them online. I listen to a very wide variety of rock, pop, blues, soul, alt country, acoustic, indie, etc. music, including some bass-heavy electronica (Brian Eno, Thievery Corporation, Moby, Groove Armada, Massive Attack, David Holmes, Mylo, etc.), and the Atrios pair very well with unamped iPods, which aren't the most bassy players around ... but the sound is "bigger" with the Atrios than it is with some other earphones. Excellent value for the money, as well. Check out the Head-Fi thread ...
Also, I haven't heard the Sleeks, but they come highly recommended by some Head-Fi posters who have owned the Future Sonics.