I have heard no soundcard that has the quite the clarity of a good quality tonegenerator when it comes to MIDI playback.
/me likes my rackmount.
Apex Pro from AVM Technologies was a Kurzweil synth in soundcard form for ~$200 in 1997...OUTSTANDING MIDI playback, also had a complete instrument editor.
Guillemot also released several high quality sound cards for amateur audiophiles/musicians with high quality MIDI playback also in the same price range, usually with Yamaha chipsets.
Of course Soundblaster is crap, and all of the general gamer sound cards don't have any decent sound generation either, but these cards weren't designed with that in mind, they're more interested in getting higher sample/playback rates with higher s/n ratio.
/me likes my K2600 :-P