Well your system is higher than the game need for sure

the ram is great , the gpu is great the cpu is great !
You will run it at Max with a resolution 1680x1050 , if you see laggy the game with that resolution then dont buy anything until you check the tips i will give you : 1: check your system for virus
2: Close any runing program in background ( program that you not need )
3: Repier system errors like registry,use Advanced system care for that or CCleaner
Keeping your PC clear and healthy it will have more perfomence than that you think

but hey ... if you have money and you dont know what to do with those money then go and buy an GTX580^^
Don't tell him to clean his registry... Unless he knows what he is doing. And remember to always backup your registry's. If you don't it can lead to problems with your system being unstable. A lot of people mistake that by cleaning your system registry it somehow gives you a system boost. Although it can help the system just be cautious with programs that promise to optimize the whole computer in 1 click. Each computer is different and has it's own problems

By the way Ccleaner is indeed a good program.
Yeah, I know all that, this is my 3rd custom build... I know all those tricks

the only thing that has me worried is that I don't know if my GPU will be man enough for it :L
Should find out soon enough! Once MP demo is released -.-