Acronis does not play well with Macs. It might on a dedicated Windows drive, but I know and use Paragon Hard Disk MGR 12 $49 and also their $20 Clone OS to HDD (makes a bootable clone so you can use either disk but it is 'whole disk" OS only.
I'd get the 4-core 2.8, and not a 2.4GHz 2.4 is not standard, it might be in 8-core or something.
People are upgrading cpu to W3680 $589 DIY
RAM: 2 x 8GB with room to grow. The sweet spot for CS5.5 is to have 24GB RAM to play with so depending.... 4 x 8GB would still be possible later. And CS5/6 under Windows for some... and ability to use GTX 680 or even 580.
CS4 is not a good idea but then I have not seen anyone - it is 10.5 era version and CS5.x is now Cocoa code base plus 64-bit - that helps a lot.
www.macperformanceguide.com has a lot to offer in ideas.
Know that your Mac Pro can run those Windows apps in a VM like VirtualBox without breaking a sweat too.
I'd get it stock and then add an SSD or two as you can afford to.
OWC has SSD on PCIe $500 for 1TB.