Another Computer Question: 620w Power Supply running this system?

Your 620W Antec is sufficient to power that rig. Antec is one of the better brand names, so you can expect that power supply to deliver 620W 24/7 if needed. You're looking at about 450W at max demand (125W cpu, 220W graphics + 100W for everything else), so you do have some spare headroom.

Ideally, you should have 50-100% spare capacity on your power supply to allow for overclocking and power supply capacitor degradation over the years. You're just a tad shy on that basis. A 750W power supply would be a better option if you don't already have the 620 purchased.

Recommended Minimum PSU for that GPU is 550 watts

With the i7-950 and the 12Gb RAM, I think you may be pushing it close to the limit.

It may supply all the power you need... but for how long.

You can't over-spec a power supply, my rule of thumb... if it say 550 watt minimum... add another 150 watts to it.

This means that instead of your PSU running at 80-90% load it may be running at 60-70% load, extending the live of the PSU and more power available for the GPU when it needs it.

i dont think of a 550ti will enable you play mw3 or 2 on extremely yet possibly on medium settings i recomend getting a 560 or a 570 and the 550watt wont carry for terribly long with a video card because of the fact the video card desires a minimum of 500watts by myself so i might get atleat a 700watt PSU to be secure.wish this helped.

620W is just fine, but you will need a higher wattage PSU if you ever plan on getting a second GTX570 for SLI.

My AMD Athlon X2 6GB (ddr3 RAM) bows down to your CPU and RAM......