OK so I bought a xfx 7870 thinking I had a 600w. Turns out it's a 450w with 1 6 pin and some 4 pin molex's. So should I buy a molex to 6 pin adapter for the second 6pin power slot and be ok or should I get a new pcu. Moreover, do I HAVE to get a new pcu? Not planning on overclocking...