Thermaltake tr2 500 watt psu with warrenty for sell

I bought this PSU on 14th June 2011 with my pc from UCC.. This PSU has been serving me well but due to its limited wattage of 500W my HD6950 some time hangs while gaming.(minimum wattage for HD6950 is 550W) But still I have managed to play tonns of games but my GPU does not get the required wattage when playing Crysis2, Battlefield 3, Darkness 2, Metro 2033 etc. So I want to sell this PSU and buy another one so that I can finish those games without anymore worries. So if anyone wants to buy this PSU just give me a call. PS: This PSU is absolutely okay and can run any GPUs but within the limited wattage. If still have questions then just give me a call :)