Radeon HD 7970 - On your average system the card requires you to have a 550 Watt power supply unit.
Radeon HD 7970 Crossfire - On your average system the cards require you to have a 750 Watt power supply unit as minimum.
If you are going to overclock GPU or processor, then we do recommend you purchase something with some more stamina.
4. Coolermaster should not be on you list of desired suppliers.
1st Tier - Corsair AX / HX series (except HX1000 and 1050), Seasonic X Series
2nd Tier - Corsair TX V2 Series, Antec HCP / HCG series, XFX Core Edition, Seasonic MD series
Other liens from above manufacturers like Corsair TX suffix M, Corsair CX, Antec Basiq, Antec Neo etc are ones id skip