In terms of bang for the buck
I found this to be my best bet when I upgraded 2 months ago. You don't have to use both processors right off and if you decide you don't need the second you can make about $50 back on your purchase price by selling it. This company might even allow you to just get a single depending on their stock situation. The drawbacks are the MB needs a case that will take and EEB size board and this particular version, the 2600CPJ, does not have all the drive ports built in as some do. It has 2 6GBS ports and 4 3GBS ports. This didn't bother me because I already had 2 HBA (Dell Perc 310) cards in IT mode from my previous box but it is an expense you have to plan for if you buy this board. I'm really happy with the performance and if for some reason I need a bit more performance in the future it will take V2 CPUs and I can easily add another 64GB of ram.