The 660s motherboard will support up to a 3rd generation core i5. This will be more then adequate for a budget gaming rig.
Now as logain stated, the tower is going to horrifically hold you back in upgrades.
You can reuse the motherboard, your hard drive, cd drive, windows OS, and possibly even your memory (if you have 6-8gb already)
You will need an i5 3xxx processor, a new case, a new power supply, possibly new memory, and your video card.
If you can tell us a budget then we can put together something for you.