Help with build please :D

Hello :D

I'm building a computer and I need help building a computer, I am using a gtx 560 ds ssc as designated graphics card and gtx 550 ti sc dedicated to physx (just had it laying around). Anyways I want to know what kind of motherboard and cpu I could get togther totaled to around 300-320 dollars additional. I am currently considering the Gigabyte 990fx GA-UD3 + AMD FX 8120 but before I purchase it I would like some opinions. Also lastly, I am also considering getting windows 8 oem instead of windows 7 because "it's 5-15% faster on games" but am not sure if my drivers would work with it. Thanks for reading ^^

http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.1094314

 

Although Windows 8 is a little faster even Logan says hold off on purchasing it. There are a lot of problems that need to be straightened out by Microsoft particularly for desktop computing. Logan suggests waiting until the first service pack comes out.