If you are going Win 7 Pro, then it doesn't make sense to waste the RAM slots like that. Stick with Home Premium if you are only going to max out at 16GB. But your mobo supports 32GB and as people have said RAM is cheap. I would get Gskill Ripjaws at 8GB sticks.

I've always have been an intel fan. I would say go i7. I also agree with the GTX 680. If you are a serious gamer, then it only makes sense to go with the best gaming materials. Having a good power supply is very important so I would say go with this one:

CORSAIR Professional Series HX850 (CMPSU-850HX) 850W ATX12V 2.3 / EPS12V 2.91 80 PLUS SILVER Certified Modular Active PFC Power Supply

the 650W IMO is not going to be strong enough.

What you can do is start low on the RAM and build up as time goes on.