I just bought a 4790K & an AsRock Z97 Extreme4 that I would like to overclock to a moderate degree (maybe to 4.5 Ghz) in a fairly roomy case. I'm not looking to push this equipment to its limit -- I got the AsRock because it was supposed to have good virtualization support, and the 4790K wasn't that much pricier at Microcenter than the alternatives. I would, however, like it to last a good long while.

I might stick a R7 260X (115W TDP) and a GTX 750 (55W TDP) in there, using the former with secondary GPU pass-through in Xen, although I am not a gamer and wouldn't expect either card to go anywhere near its limits.

Currently, I have an 550W XFX Bronze Core Edition of the sort that is often $27 after rebate @ Newegg. The review @ Jonnyguru and elsewhere was positive, except for some wonky regulation on the +12V.

My main question is: how much should I worry about this PSU's voltage regulation from the perspective of maximizing the lifespan of my equipment, especially the 4790K?

Looking at Newegg, the current options appear to be (prices after rebate):
XFX TS 650W $40 (gold)
EVGA 550W G2 $50 (gold)
EVGA SuperNova P2 $70 (platinum)
Corsair RM750x $80 (gold)

Should I replace my current PSU with one of these units or something else?