I'd recommend that you check out the PS's on corsair.com They have an excellent product line. A few dollars more than the lesser brands but it's a key component so buy the best.

find an online psu size calculator and input your system specs. add 20 percent for overclocking. then add another 10 percent for future expansion. that's about the minimum size psu I'd recommend. at that point, look for a deal from your favorite vendor

Most machines I have built, are the ATX form factor and get the highest wattage supply I can find on the planet.

A Coursair AX850 should be plenty for your machine, but you get over 1000 watt, they are usually longer, so be sure your case will accommodate it.

They can be had to 4000 watt, but consider, the 850 watt is like $240,, the Cisco 2000 over $1000