Thanks for the info. I am looking to be doing a bit of over clocking so you think I should be going for the Pros? Also I will have an ssd so will the caching be worth it? I do no video encoding or decoding and the on board video card seems to be a bit of a waste to me. So in my situation would the P67 be best for me or is there something else I am missing about the z68.
Overall, the better OC'ing 4.2GHz and higher is best on MOBO's with 12 or more Phases to the CPU. Those (3) will allow a lower, aka obtainable, vCore; Lower vCore = Lower CPU temps = longer CPU lifespan.
From the (3) above pick the cheapest, if available, COMBO. Otherwise the P8P67 PRO (REV 3.1) is the cheapest typically.
SSD Caching - IF you have a 120GB or any SSD >64GB then don't use it for SSD Caching; 64GB is the limit (or as some funky partition). Otherwise if you have a small SSD e.g. 20GB~64GB then yep it's best as a caching SSD with the Z68.