1) look into a Creative sound blaster EXTERNAL soundcard. Make sure to get one that can record & playback 24 bit, 192 Khz sounds....
you will want an external model as to keep it away from the PC's fan*.
Some models have a fiber-optic output, so your stereo's gotta have an optic in....I was bummed to find out my soundcard doesnt have an analog output.
2) Budgetting$$$.....everyday PCs have fans...more fans..more noise.....so nowadays kids are making these water cooled PCs. they are bad ass and utterly quiet. If you got a good job, go for the gold, build that water cooled bad boy. even better use anti-freeze instead.
3) options: hard drives....big ones. You could take your music and store it on hard drives....the limit is about 4 or so Hard drives....but if youve got big dollars you could get the 300gb capacities... also the latest HDs use a new faster connection...at the time I forget the name....you would need a motherboard that can handle the new connector.
Best of luck. if youre looking for to have one built I can talk to my dad, because we have put together quite a few in our time.
-Ryan