Well I will be starting a build in a few hours with a 2600k and twin factory OC'd 560's. I used an 850 watter though could have easily gotten away with a hi quality 750 watter (XFX Black Edition, Corsaie HX or AX, Antec CP or SG, Seasonic X).
Obviously, adding components requires more power. Further, you need to be very careful calculating the correct PSU size. Meaning if the calculated use is e.g. 550W then you need to add a minimum of 30% to allow for electrolytic capacitor aging and even more if you plan to OC either or both the CPU & GPU(s).
As above if the requirement is 550W X 1.30 = 715W so look at 750W.