Hi!
You are very well informed.
I will recommend 2500K over 3570K because new Ivy bridge CPU's are hotter than Sandy bridge counterparts, and they have less overclocking margin.
Intel put cheap thermal grease between chip and IHS probably because AMD
don't have competitive product in this moment.On Sandy bridge there is soldier.
http://translate.google.com/translat...11_532119.html
About GPU, yes gtx670 is futureproof and a good buy, but gtx560 Ti runs CloD very well with almost everything maxed out.I saw some nice price drops for gtx570 recently.
Quality 600W PSU is more than enough (Seasonic, Corsair...).
Assuming that buying OC'ed PC is more expensive than building it by yourself,
if you have done that before I'll recommend you second solution.
OC'ing i5 is very easy.
You can install Win 7 on the top and use both systems.
Good luck!