I've been mining coins with my HD7950 lately, and I'm planning to add in two more R9-270s. My specs are as follows: Sempron 145 underclocked/undervolted @ 800mhz 1v Asus CHV Crucial M4 2 fans generic 4GB DDR3 ram Corsair CS750M 80+ Gold I'm somewhat certain that it can accommodate two more R9-270s. But I just need a second opinion just to be sure. I calculated it quick using an online psu calculator and it totals just around 550w. Now my HD7950 is slightly overclocked to 975mhz from stock 800mhz with a .01 increment on voltage. I'm planning to oc the 270s to 270x speed. Is my psu sufficient? If it is, is it ok to run it at around 80-85% load all the time?