Desktop

Thought he Video Card is only PCI Express 3 so it might be a bit slow.

Looking over the specifications for both the motherboard and the video card, I think OH Smeg was just typing too fast.

The PNY GTX650 card will not run as fast as it can because the Gigabyte GA-970-D3 motherboard only supports PCIe 2.0. Therefore, you will not have the full bus transfer speed of a PCIe 3.0 slot.

Looking over video card specifications, you will need to spend more money and consider a larger power supply to upgrade to a faster card like the GTX670. But, you would still have the limitation of the PCIe 2.0 slot on the motherboard.

Here is an article with speed and power requirement comparisons.

http://www.hardwaresecrets.com/article/NVIDIA-Chips-Comparison-Table/132

The GTX650 looks like a pretty good compromise between performance and power requirements.

Chas

Is your PSU a Coolermaster or Thermaltake X2 or some such? No-name type PSU put out a lot less than they are rated.
Now, I just sold a system with a 500W Thermaltake TR2. The system was an i7 920 on a Gigabyte X58 UD5 board, and a GTX 650 Ti. The processor was overclocked to 3.8 GHz, and I ran Prime95 on all 8 processor threads for several hours with no errors. Running Furmark graphics benchmark, my graphics card went to 89 degrees C and my processor to 74, so make sure you have good cooling. I was running a 200 and three 120mm fans plus the Coolermaster Evo 212.
All this on a 500W PSU. If you are going to go hard, then, just to be safe, get at least a 600W, but I suspect 500 might be good enough for most gaming.