I don't do any of the things you do with your machine, I just crunch

I suggest you take a look on ebay where you may find more e5 26xx ES processors that you might expect.

You can save a bunch of $$$'s but there are some things to watch for. You want to get the C2 processors or failing that maybe C1 stepping for one simple reason. .. Companies like asus with their z9 pe8 board switch off the ability to run es cpus with the later bioses unless it is c2.

earlier cpu's may not quite be set right to run certain ram types / speeds and they might also not turbo up the same amount as retail

I mention this option so that you might save a buck or two or perhaps target your cash differently.

I'm running both the asus and a supermicro with the older C0 cpu's and although very cheap (I paid around $300 ea.) compared to C2 silicone the, rules are different quite often.