Threadripper isn’t a bad idea, but I feel there will be fewer choices from manufacturers and in the used market for motherboards with IPMI and other server features.
I’ve been trying to do some more research and there is a good post by kris (SVG of Engineering at TrueNAS) here: Samba Multichannel Core/Sclae - #5 by kris
But unfortunately there still aren’t that many details/test results.