I am going for a Sapphire Nitro 390 and before I get it (Christmas) I want to get a new psu. I am currently using a cx600. I don't really want to risk it smoking and hurting other components.
See here PSU Tier List Take the tier 1 if you can or tier 2 at least
Corsair RMi,HXi, AXi
EVGA SuperNova G2 / P2 / T2, Supernova GS, Supernova PS
Seasonic X Series
XFX Pro Series, XTR Series, XTS Fanless
With the EVGA SuperNOVA 750 B2 the OP would have to shell out $89.99, then apply and wait for approval and many weeks before getting the mail-in rebate.
If they're willing go through that then the EVGA SuperNOVA 750 B2 is the way to go.