i7 option?

[Buildop]

Hello,

I am based in the UK. I would really appreciate some help. I am looking for the most cost effective CPU and motherboard combo for the following:

1) i7 sandy bridge (with over clocking)
2) i7 ivy bridge (with over clocking)
3) i7 sandy bridge (without over clocking)
4) i7 ivy bridge (without over clocking)

I look forward to your input. My current build proposal has an i5 3570k and wanted to see if going to an i7 would be feasible for me. Thanks for you help.

 

[Buildop]

I will also be using applications which can make use of multi threading, I look forward to further input, thanks