E-Mu 0404 or 1212m are good sound cards. You'd need a lot of adapters to run your E2s from them, though, without an amp. You would probably thus want to spend some money on a, say, CMoy or equivalent to go with the soundcard.
Some of the M-Audio are supposed to be nice, especially the newer AP192 (I think that's it). They also, I believe, have some form of built-in headphone amp, if that matters.
You could also consider an AV710 for ~ $25, and then with the remaining money pick up a Pimeta.
Anyways, just to note, if you do get a new soundcard, you DON'T want to plug your headphones into the speakers still. That's just going to degrade the sound; they're not precisely high quality. You'd be better off just plugging the things straight into your soundcard then through your speakers, whether or not you get a new soundcard.