Hey man,

I don't want to steal your thunder or anything, but you should do MUCH better than 20fps on that rig. My machine is inferior in every way, and I tend to average 40+ on my main at 2560x1600 (with 4 clones, 8x6 on a 16x12 monitor).

I assume you've cranked everything down to minimum on the slaves? One thing that helped me out quite a bit was disabling vsync. Yeah, the tearing kinda sucks (and it's really noticeable at 25x16), but it massively increased my fps. Might want to give that a try if you haven't already.