Both the 2009 & 2010 have replaceable Processor boards from single to dual. I can't yet find the part numbers on the new machine but I've heard nothing about a change in these machines. The dual board should run about $400 and should change out readily. I am currently working on the repair guide for these machines but this change is just a matter of pulling the two levers and removing the processor tray support plate and changing the board. Here's the parts blow up on the 2010 machine: http://www.welovemacs.com/mc250lla.html
If you decide to also go with a RAID card, the one directly from Apple is $699 or half that from eBay or me.
I have recently found a company that is building really powerful upgrades for the 2009-2012 MacPros. Such as a 2010-2012 12-core 3.46Ghz Westmere 64Gb
Here is their eBay listing: http://www.ebay.com/usr/brgins4sale?_trk...