Thanks for the replies, just to clarify my situation....
I currently have a hex core and have a buyer lined it up for it. I have been offered the 12 core at a great price, the difference between the two is $300.
I'm just not sure if I would notice the performance hit on the single core operations. I use some pre-press software by Esko Graphics, all single core programs. Between Aperture, Final Cut X and the Esko software the usage is evenly spread making my decision that bit harder.
Any more advice appreciated.