An overclocked gpu won't take more power unless you adjust the voltage, same thing with the cpu, but they will both run hotter. I wouldn't buy an OC edition GPU though, you can save the money and buy a normal one and easily overclock it yourself.
I currently have:
Core i7 2600k 3.4Ghz + stock heatsync
Windows 7 Home premium
Biostar TH67+ Motherboard
I want to add a
GTX 560 TI SC
and overclock the CPU to 4Ghz
something that was missed earlier - h67 chipset does not allow cpu overclocking. it only allows integrated gpu overclocking. if you get an h67 motherboard, you won't be overclocking the 2600k to anything higher than stock speed. i dunno if you mistyped your mobo model number.
if you want to overclock the cpu, you need a motherboard that allows cpu overclocking, with z68 or z77 chipset. look into asus z77 v pro or asrock z77 extreme4.
when you oc the cpu, it uses more power than it's typically rated for. the stock hsf is designed to dissipate the amount of power defined by the cpu's tdp (in this case, 95w). that is why, for overclocking a 3rd party hsf is usually preferred. a cooler master hyper 212 evo will let the cpu oc and run cool.
instead of a gtx 560ti, you can look into radeon hd 7850, like asus dcu ii or msi twin frozr, unless physx and cuda are your priority.
Hello, I have another question. IF I wanted to get the HD 7870 Twin frozr Ghz edition which is 2 6pinned would those power supplies work or would i need a better one. Also will there be extra cables for an SSD?