Currently using a Phenom 9600 quad (black version but haven't overclocked it) and running 4 instances on 1 machine (4 gigs ram, GeForce 8800 GTS). I wouldn't say its amazing but it definitely smooth enough for 4 - setting the affinity for each instance specifically worked best. Unfortunately my monitor situation is crappy since I have a single 19" lcd to work with at the moment. I've got a Geforce 7900 GTX sitting on the shelf which I'm wondering if I can take advantage of with another monitor to spread the crunching out a bit?