I know for 2010 the W3670 is a lot cheaper and only 4% slower $600 3.2GHz 6-core.
Intel® Xeon® Processor W3670 (12M Cache, 3.20 GHz, 4.80 GT s Intel® QPI)with SPEC Code(s)SLBVE
Intel Xeon W3670 3.20GHz Hexacore Buy.com
W3670 Upgrade MacRumors
If you need more than that in two years, time to swap the systrem. A year from now, after Intel readies Ivy Bridge Xeons and new socket, LGA2011, there will be other goodies to throw in the pot: PCIe 3.0 for one and other features people are waiting on.
OWC Turnkey is expensive, maybe if your system can turn around the cost in doing more work to pay for itself. Even though it was only released two years ago, you don't see firmware updates to improve and add support for new processors and steppings.
Not a real lot of apps. Which is why FinalCut X had to be redone to use more cores and memory, it isn't automatic and Grand Central just lays the APIs and groundwork.
The $1200 extra BTO 3.33GHz 2010 model is the sweet spot.