Re: old parts
The card will probably sound better than your onboard. I have the same card and it sounds better than my Asus P5W DH Deluxe, which is supposed to be a home-entertainment motherboard.
You can throw away the graphics card and the PSU. I don't know if RDRAM is still worth something; you should look it up.
You may be able to sell the CPU.
The hard disk is fine. It will perform close to a newer drive.
CD/DVD and floppy can be used if you need them. Other than that, they are worth nothing.
TheMajorMMX - Intel P200 MMX @ 225Mhz - V-Tech (PcPartner) Baby-AT mb w/ Intel Triton TX chipset - Nvidia Riva TNT2 M64 w/ 16MB - 256MB M-Tec SDRAM - Still running.....