I have 4 gigs in mine, but I see no speed boosts from when I had 2gigs doing Audio work. (8-10 tracks @ 44.1 or 96)..somewhere I read that windows applications cannot address more than 2gigs of RAM? I dont remember..anyway, 2 gigs should be more than adequate. FWIW, this is with an AMD Athlon 64 3500+ CPU.
(Which I am selling, btw, just got a Dual Core 4800+..Samplitude and Sequoia 9(the DAWs I work with) can both address dual cores.