|If you're planning on using Nvidia GPUs, you won't be able to use different GPUs together in SLI (You can use two different Nvidia cards if one is dedicated to rendering, and the other one is dedicated to PhysX, though there isn't much performance gain). If you want SLI the cards must be of the same model.|
If you wanna use AMD cards together you are a bit more free to vary with the model of your GPUs as they utilize AMD's CrossFire technology.
I am not sure what you mean about "share connection" between your integrated graphics and GPU. But if you mean using it in the same way as with SLI or CrossFire, I doubt it's possible.
The amount of supported displays can be found in the GPU specifications.
Going for anything else than x16 PCI cards isn't worth it if you're going to play games.
Don't worry if plan A fails, there are 25 more letters in the alphabet ;)
message edited by RainBawZ