To toss in two cents.

Quad-Core is not necessary, I have a 2.2GHz Athlon 64 X2 that rocks the boxin.

I use 4 GB of RAM (not x64 so I don't see all of it, I know I know, I multiboot to other non-Windows 64 bit OSes)
My vid card was a 7800GTX and is now ann HD 3870X2.
I run my WoW installs off of 2 different drives for performance.

I have no issues and can run through Org without losing any fellows.

Keyclone is AMAZING at managing my FPS (back windows are limited to 15-20) and my card handles the rest :-D