Would a good 650W psu power an overclocked i5 4670k and a gtx 770?
Yes. What PSU were you thinking of getting?
Even quality 450W PSU would be enough. Just get 550W and you'll be fine with any single GPU setup.
I was thinking of getting the SeaSonic SS-650KM
That should be a great PSU. You don't necessarily need to spend that much though. I use a Corsair TX650
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139020
While not quite as good as the Seasonic, it should still perform well.
That looks like a good psu. I think I'll get this instead and save myself some money. Thanks Morgoth
No problem. I've been running my overclocked i5 3570k and HD 7950 on it for almost 15 months now and I've had absolutely no problems.