Which PSU for i5 + GTX 970 (how much W?)

[ShakeNBake]

i5-2500k (overclocked)
Single GTX 970 (potentially overclocked)
4 case fans with LED's
2 hard drives, 1 SSD

550W enough, or need more juice?

Corsair or SuperFlower?

Thanks
- Shake

 

[ShakeNBake]

ok thanks guys, I had an eye on that one, reviews look really good for it.

one more question: in HWMonitor, my power readings for CPU are fluctuating quite a lot (1.28-1.32V), despite CPU voltage being set to 1.30V in motherboard BIOS. is this usual, or sign of a power supply that's on its way out? I don't remember seeing this in the past, but maybe an update to HW monitor or something made the readings more accurate?

I have an OCZ PSU, but it was one of the decent ones, I have had it for quite a while now, at least 5 yrs, so just wondering if it would be a good idea to get a new one just to be safe?