CPU recomendations?

[635600]

After upgrading my computer, im having trouble with RTS games. I cant get very many men on the screen without lagging up. Does this require a new CPU upgrade?

Windows 7
Studio xps 7100
AMD Athlon(tm) II X4 630 processor (4CPUs) ~2.8Ghz
7168MB RAM
GeForce GTX 560 ti
Directx11
1920x1080 resolution

Are these cards universally made for any system or are they picky?
Im willing to spend $150-250 if this is what i need.

 

[notlim981]

7168MB RAM

Is this 8GB of RAM? I didn't know the 560Ti shared memory with RAM.

What exactly do you intend to upgrade?