At least with graphics on the chip for the 2600k you can look for a gpu at any time.
If you get the 2600k oc'ing will make gaming better and if/when you sell it the 2600k will be worth more, easier to sell
I used windows 7 prerelease candidate for a year on 1 rig.
Just remember that you can't save anything when you go to another os from prerelease(I think)