Alternative to a new power supply if your short on watts with upgrades to your pc.

If your power supply does not have the wattage for the components you add such as Video cards etc.. I purchased and installed the FSP Group Booster X5 450W Independent/Supplementary SLI Certified CrossFire Ready Active PFC Dedicated Multi.GPU Power supply that fits in your 5.25" drive bay.
I was hitting my power supply max with my pc and did not want to spend the cash for a 1000 watt or over power supply and put this bad boy in. I connected it to my EVGA GeForce 295 CO OP video card and It works great! Now I'm running 1200 watts with no worries.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817104054&Tpk=fsp%20group%20booster

Power Supply Calculator: http://www.antec.outervision.com/

MY PC with new power supply in top 5.25" bay: