Take care installing RAM into that motherboard. I had it but got it exchanged (not for this reason), and I noticed it's not quite ATX sized. It's got different stand off positions and it doesn't have much support when sticking RAM in. It's pretty flexible too.
There are several factors involved in determining what you will get for FPS out of your computer.
First , the game that you are playing.
Second , the resolution on the monitor.
Third , the settings in the game.
Fourth , sometimes the cpu will be a determining factor.
Lastly the video card which is actually the most important part will have a huge part in what you will get.
So all of these things will determine what the FPS is that you will get , for example you want to play BF3 and you want to play at 1920x1080 and the in game settings are set to ultra , in this case the fps will be on the low side because you will be taxing the video card real hard and you might only get 25 fps which is barely playable. So then you would have to lower the in game settings to medium and the resolution to 1280x768 and you might end up with 35 to 40 fps which now becomes very playable.
The game COD MW3 is a different story because it's not as demanding a game so you can have the resolution set to 1920x1080 and the in game settings on high and be getting 60 fps and have great gameplay.
So because there are so many different combinations of cpu , gpu , ram and monitor resolution it's hard to say what you will be getting for fps and the only way to know is to run the game on your computer and see what you end up with and what kind of adjustments you will have to make. The good news is that you have a good video card and a good cpu so you should be getting some good gameplay and only with the most demanding games will you have to lower anything.
A GTX 480 for $200 is a very good (and hot) deal. But get the 560 Ti unless the 480 has a custom coooler (I'm looking at Gigabyte and MSI).
Or, if AMD is an option, get a Radeon 7850 with the $30 you saved on the motherboard. Runs much cooler and quieter. You could probably Quad-Crossfire them with a 650W PSU. And, it can match the performance of a GTX 580.
This graphics chart should help you see where cards fall in comparison between Nvidia and AMD.
The GTX 480 is two levels above the 560 and is at the moment one of the better deals going. When it was released the GTX was a flagship video card like the 580 was when it was released , while the 560 , 560Ti , 550Ti , 460 and others were not so a GTX 480 is a top quality card and would then perform better then the 560 and even the 560Ti and would be on the same level as the 570 but for a lot less money.