It would be helpful if you listed a budget amould because with that info we can rearrange the build for you to get the best gaming experience that you can get for what the budget amount is. By looking at the build as you have listed it there are a couple of things going aganst you for gaming performance.
The video card is not a good choice and there are a lot of complaints with the performance of the 550Ti. While Nvidia cards are good in some games and AMD cards are good in other games sometimes certian cards are just not good performers. A 6850 or 6870 would be better choices.
The AMD cpu's are known for not being able to match up against Intel cpu"s and while the draw of the AMD cpu's is low price you end up with low performance also. For $80 you get a three core cpu that's far down on the list of gaming cpu's. So this is where the budget amount comes in to see if a better cpu can be had.
Intel Core i3-2100 Sandy Bridge 3.1GHz LGA 1155 65W Dual-Core Desktop Processor Intel HD Graphics 2000 BX80623I32100
$119.99
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115078
This is a dual core with hyperthreading so you end up with four threaded cores , so what that means is that when in a game the OS can use two cores for the game and now it has two more threads for programs running in the background and they are not using resources that would be for the game.