I have a i5-3570, DVD-RW drive,and 3 case fans. I am planing to get a Nividia EVGA GTX 670 FTW 2 GB. I have a 500 watt power supply from Corsair ( CX500M ). Should I just upgrade my PSU with my graphics card, just leave the PSU alone, or just save $100 and get a EVGA GTX 660 Ti 2GB Superclocked?