Good music soundcard

Here's another vote for the E-Mu 1212M (or 0404M, I guess). The difference in audio quality between one of these and your typical Audigy/Soundblaster card is HUGE.

Try Lynx Studio Technology, M-Audio or RME-Audio for hi-end soundcards.
For USB to Digital Coax/RCA interface converters;
Xitel Pro-HiFi-Link or Empirical Audio USB Off-Ramp & Freeway.

The most highly regarded sound cards in the under $200 price range would have to be the e-mu 0404 and the e-mu 1212. If you want to spend more than $200 I suggest a firewire or external DAC solution. Technically the e-mus are professional audio cards but they're perfect for the requirements you've stated above. Good drivers (including ASIO), lots of community support, even a community of modders for the tweak-crazy :)
The head-fi computers as source forums have a lot of information including featured reviews of these two cards which will explain why people like them. The high quality DACs and the ability to have non-resampled audio in particular make this a good choice if you want an internal PCI audio card.