You don't want to skimp on your power supply when overclocking. The brand name itself isn't as important as the ability of the PSU to deliver the rated power at the specified ranges for each output. Having said that, generally, the more generic brand name PSU cut corners in manufacturing to deliver a unit at the lowest possible cost resulting in a PSU that is not as able to consistently meet the demands required in OC'ing. Measure the voltages on your rails to see how close they are to spec. That will tell you a lot more than just looking at the rated output and brand name. W/o sophisticated test equipment where you can measure the rated output under load and measure the clenaliness of the power delivered, that is about the best you can do on your own.
In the end, you'll want to spend the bucks on a decent unit- go to
Tom's Hardware Guide and read up a little and wait for others here to suggest what they like in PSUs.