I rest my case.
Buy the best PSU you can afford because you don’t want to not be down and not able to play because you used a cheap PSU and had it damaged one of your components. It can and has happened before since cheap PSU will not try to even out small power spikes and sags.
Most newcomers to the PC world, often overlook one of the most important aspects of a stable system. The power supply never garners as much attention as it deserves. Afterall, a poor power supply can render some of your hadware useless, or destroy your machine as a whole. "How do I choose a power supply?", you say?
Most people go by the wattage rating that is advertised somewhere on the power supply itself. Thats all it is everybody, just a rating. Most of the power supplies on the market today are rated at their peak output, which means it puts out that much power when its begging for mercy....ready to take your rig with it. Wattage means absolutely nothing. Heck, a hair dryer puts out 1200W, do you think it could power your computer? Think of a cheap 600W amplifier, but put it up against a quality 400W and it gets killed. Quality is what we're after everybody.
If you've boughten a cheap PSU, and it hasn't gone out on you, you're lucky. Sure, they probably do fine more times than not, but you don't want to take the chance of damaging hundreds of dollars of equipment, just to save $40.
EDIT: Newby, I found a great PSU for you:
http://www.newegg.com/Product/Product.asp?Item=N82E16817153023993 reviews, with only complaints of a bad PSU upon arrival, and too bulky of cables. Best rated power supply for your specific needs, and they have a weekend special resulting in it only costing $27.99 after a $12 mail-in rebate.