Any reason why you would only by from big brands?
Yes, There is a reason to purchase only from reputable brands. The PSU is THE single most important component in your system. If that fails it can take multiple other components with it costing you a lot of money and time to repair/replace. That's why it's important to buy from manufacturers that build and test their PSU's to rigid specifications and that make sure that the PSU can perform to those specifications. Many manufacturers spec their supplies to meet output wattages and currents that simply do NOT meet their own specifications. Seasonic, Corsair, XFX and some Antec models are known to perform at or above their specs and are, therefore, reliable. There are other PSU's from other brands that are good but I KNOW I can trust those. Personally, I only purchase Corsair (lower cost) or Seasonic PSU's.