if you have a fairly high budget, do with intel, my next build going to use AMD only because pricing and the fact i HAVE to be able to use IDE, but anyway, go with intel on this one, the pentium g860 (i think, cant remember if that or g680, something liek that) could do as well if not better than the FX in some cases. And that 550Ti is a pretty good card usually, depends on what your budget is, and what model you get, some 550Ti's are overclocked more by the manufacturer and have more performance than others. also the 6870 (on newegg) is actually like 20-30$ more than an average 550Ti, so again it depends on budget.
I'd swap from AMD CPU to Intel and from Nvidia to AMD of the GPU. Also 8 gb is overkill still unless you run multiple instances. You'd be better off with 4gb of much faster stuff than 8 gb of the slow stuff.
It's a nice build IMO but it's not very solid. First of all u have to get a better gpu. AMD has better ones in that price range. I have a sapphire 6850 and it's better than most people think. I run it without OC'ing and get 40ish fps on BF3 high setings 1920 x 1080. Secondly the CPU. With that money u can get a nice i3-2100 and it will perform better. not by a lot, but better is better.
AMD Phenom II x4 970 (stock) / Sapphire 6850 / G. Skill 8gig low voltage / Samsung 1TB HDD / ASUS m5a87 / Corsair cx600 / Rosewill Challenger
the cpu is good, you will be able to have playable rate with it anyways, no need for intel, imo if your going intel just my honest opinion, those at i5 or above are best, but if its bang for buck, i5 2500K or the i5 2300/2400 non K if you can't spare some cash but hey they ain't that bad, but i do agree amd 6850 is actually very good, 6850/6870 in my opinion goes up there with 560ti well price/performance wise its really good, you can stick with that build and just replace those useless gpu to 6870, if you plan to over clock it go with cooler master hyper 212 evo, oh and if i were you ditch that psu, go grab some nice seasonic or corsair or antec 500w or so