I use one system. quad core q6600, 8GB crap ram, ati 4870, intel SSD (the newer, economy model). I get very good performance 5 or even 6 boxing.

Of course I have quite a few optimizations. I've done just about every little optimization (registry changes, services disabled, etc.) you'll find on various websites. I do not run a resident anti-virus (you know, the modern ones that run like 15 processes and hook into all system calls including I/O), because they absolutely murder performance, even the lightweight ones. I run it manually if I need to, like the old days. But that was the biggest performance boost, other than the SSD, that I've ever seen.