The only thing I can think of would be upgrading the video cards (outside of what others have already told you). I'm running the new i7 processor with 9 gigs of ram and am experiencing very little lag. The only thing I get that is noticable is in Dalarn it just feels slightly more sluggish (but it isn't chopy and laggy at all). My video cards are two nvidia GTS 8800 GTS with 640MB ram.