On looking at your specs,,all i can say is,,why bother? Only upgrade i'd suggest is your CPU. And the only reason i say that, is because i just bought(upgraded?),my CPU to a lowly AMD XP 1700 with JIUHB stepping and punched it up to 1700Mhz(XP2000+) and it runs at 42c and very stable. And you can get it(if you hurry ) at newegg for us$53.00 with free shipping!!!
Bottom line? Money ain't everything,,ya' know?