You should be fine with that system both for CPU and PCI-Expresss. I think the most you can put in it would be a Phenom and possibly a Thuban depending on the motherboard. I don't think its compatible with AM3+ CPU's.
There will be come games that might be hard on that CPU (some games are very CPU defendant) but you should be fine with somewhat lowered settings.
Also 750w is a lot, you don't need that much but you cant go wrong with extra.