Currently, I have a dell percision T7400 I leave running.
Can support up to 128G of ram, (I currently have 28G)
Supports dual quad xeons @3ghz (I am running a single currently, but, have a second in the closet)
PCI-E x16 (We have successfully used these as gaming rigs.)
4 internal slots of 3.5" sata. I added 4 hot swap bays on mine as well.
I have a machine that I'm relatively proud of... 10 disks, hw raid card (in IT), 16G ddr3 ecc ram and the e3 1231-v3 and it maxes out at ~190W. . Idles much lower.. If I ever let my drives spin down I'm sure it'd drop a lot lower. its a bit of a beast and super reliable.
Only had one problem with it really and it was remedy'd with a pci intel nic
It runs my handbrake scripts, serves plex (REALLY well), media management tools, mysql replication vm's backup targets, clones ... some of everything. my vote for an e3!