After all that discussion - and regardless of what *could* be used - there simply isn't an alternative processor in the Bloomfield family that will upgrade your performance by any significant amount. The high-end processor in the family is the Core i7-975 Extreme Edition, which would represent only a 12.5% increase in clock speeds and less than that percentage in overall performance gain. Increasing the amount of memory available could potentially make more of a difference in overall system performance than this processor upgrade would make (if this upgrade is even supported). Regardless, the overall performance gain available does not seem worth the high cost necessary to make this move (if it is even supported).
Bottom line, I would consider this another of those "throwing good money for bad" situations;. I believe that your money would be better spent coming forward a significant number of generations, replacing the processor and motherboard (and memory, if you come far enough forward that DDR4 is necessary) with something far newer. From the standpoint of software compatibility, you would be moving to a generation that is formally support by and for Windows 10.
Hope this helps,
...S
