Core i5 based Gaming PC questions?

The i5 will be fine without OC. I built a system a couple of years ago with a Q6600 and it ran Crysis fine without OC so the i5 will do it. I did eventually OC it and couldn't tell a difference either way with games. The video card is what will matter. I wouldn't go the the extreme of running 2 cards just 1 good one. You could spend $600 on a great one and it'll be out of date in a couple of months. I did that and now realize it wasn't worth it in the long run. EVGA will let you trade up if you buy from them so that's why I like them. Just go with something 1G midlevel like a GTX260 and you'll be good. You can always OC the vid card as long as you can keep it cool. I did that with my 8800gt back when I first built it.