Amount of Power needed?

With those specs, assuming a SATA hard drive, DDR3 SDRAM and a DVD-RW optical drive, at 100% load you need 400W -> http://extreme.outervision.com/PSUEngine

So 500W should be fine, you always need to add some wiggle room for expansion. It never hurts to buy a more powerful PSU, especially if you plan to do an SLI configuration with two GTX 660s in the future (provided the board supports it)

Remember, the PSU calculators give you estimates. Each company has their own formula, some are more conservative than others.

Those things are never right. If you go to 5 different ones, you will have 5 different answers. I would recommend a 750 watt power supply. That will give you plenty of power with no worries. I use an 850 watt for an i5 and Radeon 7770 - it's overkill, but I don't have to worry about power no matter what I do or what I add in the future! :D

~Cindy! :)

Since I don't know the specifics of every part its a little harder to estimate but I looked up the parts that require the most wattage and powerful PSU and assuming that it looks like you should go with a 550-600 watt with a 80plus cert to power your system while increasing energy efficiency/costs.

If you plan on added another graphics card to run in SLI later on, then you should go for something in the 800watt area.