1 GBE is enough. no more drives - replace with higher capacity if storage requirements go up (don't see that for next 3 years for sure)8 drives will allow a large amount of boards in smaller sizes to be used including mATX which allows smaller cases
So next question is - Expansion capabilities.
Do you want/need 10GBe or multiple (more than 2) 1 GBE NICs ? If you have only 2 concurrent users 2 x 1GBe should suffice
More drives in the future? Or will you replace with larger ones if you need more space?
How many VMs do you want to run? What kind of VMs? -> 64 Gigs should be fine if you only have 1 or two smaller VMs
That will allow to pick any recent Intel generation (including E3 v5/6, limited to 64)
If you need more (->128) that still leaves XeonD or C3000, even more (->256) C3000 or Xeon E5
VMS - 2 windows and 2 Linux servers along with plex - 2 streams max.