Purchased a Supermicro 2U server with a 14 core 2690 v4 CPU for barely more than the price of the chassis alone. Bumped the configuration to 256GB of RAM for just $125 more.  

It should be a healthy upgrade from the 6 core 2013 Mac Pro it will replace. Eventually I’d like to upgrade to an Epyc Rome/Milan build in the same chassis, but I figured I might as well try this setup first. If it’s not quick enough, I’ll just buy the new motherboard/CPU and reuse the RAM.