MSI 865PE Neo Platinum edition($90.00) with a 3.4Ghz preston core 800 Mhz FSB ($150.00)(or higher, depending on your money sitcho), 1 or 2 gigs of corsair memory ($100-200 per gig depnding on speed of memory), dual 200GB sata 150 drives runnin in a raid config (stripe) ($150 each, 300 total)... and 2 200GB UDMA100 harddrives for backup and archival of your old music, or your whole computer for that matter (125.00 each or 250 for both, BUT ONLY go seagate or western digital, the only drive manufacturers that I have never sent back to a manu)... if you game, go with a highend radeon or geforce fx card for video, both brands have dual outs... or if you don't game and you literally want three monitors for all of the cool shit we play with, get a matrox parhelia (not good for gaming)
you said you were happy with your soundcard. add the case & powersupply of your choice and you are pimpin for less than you thought. Also, you should get much better aftermarket cooling for your pc due to the extreme heat of the faster p4 - prescott architecture...
Hope this answers ya =)
huge tip here: never forsake your harddrives or your backup harddrives or memory. newer harddrives are bigger and much faster, but they lose data easier because of the speeds they spin...