In order to run the game smoothly you'll need a quad core. As of now you can get a phenom ii x6 1090t @ 3.2-3.6ghz for about 170 or lower, I saw some new ones on ebay for only 140 dollars. You could go with the phenom ii x4 955 @ 3.2ghz, at most they should be 120 but you can find some for cheaper like on ebay or retail sites. If you want to max at the game @ 1080p minus none post effect antialiasing your going to want to upgrade your gpu also. I have a 5830 that overclocked and it played both maps on the beta at 31 fps minimum with the exception of sniping so I would suggest at least get a AMD 6850 or nvidia equivilant which is a around a gtx 560. You can get a 6850 is about 150 before rebates and is about 170 before rebates on newegg. If you willing to deal with ebay's sellers you can get really good deals on 6870's and gtx 560ti which are better than the previous cards I listed. Anyways, what is you budget? If you cannot afford both I would buy a processor first.