I've had some people tell me that if I ran 3 of my 5770's, the performance would be worse than the 2 that I am running right now. Is this true, I would think the more GPU power the better the performance.
Generally the 3rd card doesn't scale well so it is a bit of a waste, however, it also depends on your motherboard. If it doesn't support 8x/8x/8x PCIe lanes then yeah the performance will be worse than with just 2 cards.
"Looking only at averages, the chart above makes it appear that adding a third card boosts P55 performance by nearly 8%. Yet the fact that it hurts performance in some games and offers no benefit in a few others means that we’d never suggest using the P55 PCH to host a third graphics card in CrossFire or SLI. Moreover, the X58 gains 25% by adding a third card and has no performance issues..."