You can combine any CPU brand with any graphics card you could possibly want, what you need to look at the time of buying a graphics card is whether there'll be any bottleneck from the cpu ( that's not your case) and mobo compatibility ( only with PCIE 2.1 cards, not your case either as the mobo is PCIE2.0), not whether to combine Intel/ Nvidia or AMD/Ati. It's up to personal preference and the price/performance offerings from each camp at the time.
And no there aren't any extra performance improvements from using Ati with AMD processor.
AMD sends a shipment of PCBs to all card makers, then they can put stickers, change the cooler, modify the PCB without noticeably afecting performance, Modify the BIOS so the card comes factory OC'd, or do anything they want to it. All that to add better cooling performance and make it more visually appealing to the customer.
i get like 45-60fps in wow cata the only reason i want to upgrade is that the minimum card for cata is an 8600gt which is close to my card sowhtever expansion is realeased next im prolly gonna need a new card
If you are happy with your current performance then just wait until you actually need something better. Video cards are a fast moving technology and later on there will always be better and more advanced choices available for less money.