RAM for Supermicro X11

[Chris Moore]

What about energy efficiency? Skylake+motherboard+DDR4 combo is more expensive, but with 14 nm litography Skylake is very energy efficient (compared to 22 nm Ivy Bridge+DDR3). In the long term, it may very well worth paying extra for Skylake.

I am absolutely sure there is a difference, but the drives will probably be a bigger factor. The drives I am running burn about 10 watts each and the SAS controller is another 10 watts, with 16 drives, that is about 170 watts without consideration for the CPU, memory, system board, etc.
There is a cost to running a server 24x7 but if you focus on the CPU it will take a very long time to make back the additional cost of buying the latest generation hardware. I plan to stay on my system until the performance won't keep up with demand or the hardware fails. I figure that will be five to seven years.