I personally feel its important to maximize the potential of the machine you purchase by getting the most powerful one you can afford.
Also I think getting dual 8 threaded processors which give you a potential of 32 hyper threads is the best way to go when using the CS6 software.And in line with that, getting the fastest processor speed as well.
My philosophy was to get a machine that could handle any codec / project needs that were thrown at it.
I also feel the new generation of PCI-E external raids is the way to go. I get about 1000MB/sec read/write speed on my Dulce DQg2 system.
All these choices serve to fortify the performance of the Mercury Playback Engine . And that means good things for you.
Tom Daigon
PrP / After Effects Editor
http://www.hdshotsandcuts.com
https://www.youtube.com/watch?v=DxPrG3WUyz8
(Best viewed at 1080P and full screen)
HP Z820 Dual 2687
64GB ram
Dulce DQg2 16TB raid