I know what you mean about working at enterprise class scales then having to go home and slum it up with a single socket and these silly storage systems that can't handle 500k IOPS with barely a yawn... I take pictures I can drool over in weak moments to save my home power usage and wallet from certain demise.
Without gaming, you could probably fairly easily do all of the above and a typical sized GNS3 lab (at least in ESX). Dual CPU might come into play if you run ot of RAM, but I wouldn't expect CPU usage to be huge (aside from Plex, SABnzbd, and GNS3). But getting a second single socket system for that stuff would probably be cheaper.
A Supermicro X9SRA, 64gb with 4x 16gb DIMM modules (half populated for future growth), and an E5-1650 v2 would be a fairly powerful and decently affordable server. I went my route with the dual Xeon board mainly for the seven x8 PCIe 2.0 slots, not necessarily CPU core count.
I was doing pricing for GNS3 and VIRL labs (Microsoft would be similar in requirements to VIRL) and found that for massive labs, a quad socket Opteron 6262HE would be worth looking into. 64 cores fully populated and lots of DIMM slots to allow massive amounts of RAM to be had cheaply. Don't need speed for labs, just quantity. I've seen an embarrassingly large amount of VM guests jammed onto an old single socket 6 core Xeon 5600, in production workloads, just humming along quite happily.