I use the PC as my main stereo and "media centre" with the following software/hardware:
XP Pro SP1 + DX9b
Windows Media Player 9 + mp3s, CDs, movies etc
NVidia GF4 with SVideo-out
Soundblaster Live 5.1 Digital (2 speaker mode)
Sony amp
2 x 350W RMS floorstanding speakers (18Hz - 22,000Hz, 96db sensitivity
)
It does a good job of shaking the floor in my house and several doors down the road. :p