Best Processors for PE-R610 Gen1?

Sorry if it's around and I missed it but I have not been able to find a 100% definite answer to my question. 

I have a Revision 1 R610 with a single E5502. I want to jump it up as far as I can (within price reason...) I know the V1 mobo can't run any of the 130W Xeons, but I find conflicting documentation as to whether it can run 80/95W 6-core X56's. Can I use a couple of X5675's or X5670's? if not, what ARE the best processors I can jam into a V1 mobo? X5667's?


*EDITED* sry, botched some nomenclature.