I just upgraded to a Q8400. So I'm running quad 2.6, 8gigs ram, 1tb 32mb cache SATA drive. and a PCi-E 8400 GT Nvidia card. my ownly downfall atm is my video card, and I lag here and there, but it's usually not bad, and I'm normally 30 FPS on the main, 15 on the slaves.

So RAM is definetely you're point of upgrade here, sucks that you're at max the board can take.