You currently have an Intel CPU in a 775 socket. Do you know the model of the CPU? I'd imagine with a Nvidia 660, your biggest bottleneck may well be the CPU.
Honestly, it might be worth while saving up for a new PC all together. Prices are coming down rapidly on 3rd gen (IvyBridge) Intel i series (which will still be great performers for years to come). What country as you in? That might help us get some prices if you're interested
Also to note, your motherboard is not PCIe 3 compatible. Now, that doesn't mean it won't work; it just means it won't be using it's full potential!
The Antec Power Supply is also fine. I can't find the actual page in question, it gives me a 404, however assuming it has the necessary power pins (2x8pin - I think) for your graphics card, it should be fine.
I know it's not exactly what you asked for, but just my 2 pennies.
Depends on the CPU. A dual-core will almost certainly be a bottleneck; however, a quad-core, especially an overclocked quad, is unlikely to bottleneck much of anything except *maybe* BF3/CoDMW3 or later - and even that is only at high levels of detail with AA. Because I typically game at the same resolution as my desktop (1920x1080 - which is also my monitor's ceiling) I generally turn AA off, and that is with a GTX550 Ti (which has half the RAM of the 660) paired with a bone-stock Q6600.
And a GTX660 mostly requires ONE 6-pin power plug - even a factory-overclocked one. Case in point - http://www.evga.com/...=02G-P4-2662-KR
And while that's the lower-end factory-OC card, the top-end card differs ONLY in RAM loadout - power requirements are absolutely unchanged. The evidence - http://www.evga.com/...=03G-P4-2667-KR
The shocker was the lack of power requirements - neither GPU requires greater than a 450W PSU (basically identical to the GTX550 Ti).