I'll just chime in with my agreement on the RAM. I've upgraded my PC quite a bit, just for WoW:
MB ASUS K8N-E DELUXE NF3 RTL
CPU AMD 64 |3200+ ATHLON 64 512K
(4) HD 80GB|HITC SATA 8MB (RAID 0 Array)
1GB PC2700 RAM
RADEON 9700 PRO
And between the 4-drive SATA RAID 0, the AMD64 3200+, 1G of RAM, etc., the memory has been the biggest issue. This system is way above their "minimum requirements," but it still gets choppy with only 512M of RAM. With 1G, I see no slowdown at all, even in high-population areas. The only time it's been bad was during a 100+ person battle (but that crashed their server, too!)
Incidentally, Piel, I'd probably be willing to buy a stick of that RAM off of you. I'm putting together a new machine as a media server, and need some extra memory...
Spider