I always recommend a little more psu then you actually need so it is not running above 70% capacity all the time. The Corsair CX-600 for $69 is a quality Psu with 2 6+2pin graphics card power connectors, if you want a modular PSU the Corsair CXM-600 costs $79.
Ummmm... TR's 650 Ti review system with an i7-2600K sipped 143W under load.
That's 24% of 600W (nowhere near the 50% peak efficiency
) Irregardless, I'll back up the recommendation for a 500-650W PSU because it leaves the door wide open to ANY single GPU system in the future. Use a PSU calculator
if you want to plan for future upgrades. (GTX 780 Ti perhaps?
To the OP, if you're looking for something cheap, decent quality, and plenty of power for your system; Corsair's CX 430
is regularly on sale for $20 after MIR (like it is now). Impossible to beat. It's a very popular PSU as you can see by the 1,900+ reviews.
If you're looking for something nicer, check newegg.com
for 80 Plus Gold PSUs in the 500-650W range. 80 Plus Gold efficiency gets you nicer internal components and helps weed out a lot of the not-so-great units. Modular is nice if you can swing it.
Main: i5-3570K, ASRock Z77 Pro4-M, Asus GTX660 TOP, 500GB Crucial BX100, 2 TB Samsung EcoGreen F4, 16GB 1600MHz G.Skill @1.25V, EVGA 550-G2, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Crosley D-25 Case Mod