Yes it will greatly decrease your game performance when it blows up and takes your system with it. Never skimp on power supply. You can cut corners to a certain degree on anything else in the system, but never should you do so on PSU. Make sure to buy a quality unit from a well known company like Corsair, Seasonic, PC power and Cooling, and such. Even some of Rosewill's latest offerings with 80+ bronze or better are a much better buy than some basement no name from Ebay or Best Buy.