I'll be using an i5-4670k and an R9 270X and I was going to get the XFX 650W but I want to crossfire in the future and I don't think 650W is enough. The rest of my components:
GPU: Asus 7870
Cooler: 212 EVO
HDD: Caviar Blue 1TB 3.5" 7200RPM
Case: Z11 Plus
Optical drive: LG GH24NS95 DVD/CD Writer
RAM: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600
Perhaps a Seasonic G-750? You should be OK as long as you aren't overclocking a lot. I would recommend waiting until you are going to crossfire and upgrade to a 850+ PSU at the same time. Then again, I'm not sure how much power consumption the 270X draws.