Hi, hope this helps, um you plan one getting a 480? So you wantnthe top of the line in that series? (quickly,the 480's get hotter then a 580,they use more power and they perform less, with the reliece of the 680 the prices in 580 dropped allot, I dont know your budget, but an 570 out performs an 480, and in some games an pre-overclocked 560ti out performs a 480 aswell, and is cheaper, So firstly I would suggest looking at the 5sereis before going for a 480. Nothing against them, but if you can get bettter for alitlle more,then why not?). As for the quistion, your cou is allitle out dated, it will botlleneck you new gpu,but not by so much that it will make a giant differance in games, you will notice it in rendering and graphic desigh programs,mhowever,in games the performance will be botlled by the q6600, even though iit was a great cpu. Unfortunatly if you plan on getting a top gfx card, your gonna need to look at a new cpu,wich means new motherboard...and it gets pricy then. As for the card you suggested, its Evga!!! So its allready a win (anyone that differs,please search google for top sold brand cards in the world) there is a reason evga has that number one seller sticker, secondly they offer amazing warrenties. And the card looks good too.
So basically in my own opinion, if you upgrade your gpu, dont stair flat atmthe 480, it is a great card, but got replaced by 5 series, as have the 5series been replaced by 6 series, my point is you can get more performance from newere technology and not have to pay to much. Secondly,the cpu will have to be upgraded on your choice,it wont effect gaming to much if you dont, but its seriously recomended,and the i5 or i7's will definatly not bottleneck your gpu, and the new mobo will give a slight performance boost too,so except for the extra cash you have to drop, its a win win. But yeah,that evga card is a great choice overall.