The only performance hit you'd want to be aware of is if one machine is significantly slower than the others, that toon may lag behind / have latency issues. one of my setups is 4 PCs, the slowest being a 1.67ghz Atlhon XP 2000+ with 768mb ram and a 32mb video card. it doesn't have any lag problems at all. So I wouldn't be worried about everything being *exactly* the same.