Upgrade from i7 3930K help

I'm at a cross roads on this. I'd rather not dump a bunch of $ into a rig build for several reasons, but it may be inevitable.

My rigs have the P9X79 Pro motherboard and i7 3930K. Would the XEON E5-1680 V2 be a worthwhile upgrade at this point? It looks like the best of the old X79 CPUs. It would give me 2 more cores / 4 more threads and sounds like it overclocks well, but not sure if it's just wasted money at the end of 2019?
These motherboards still have everything we need except maybe M.2 if I want to get larger M.2 SSDs instead of SATA, but with so many PCIe 3.0 lanes available, I think I could use a PCIe to M.2 adapter.

If I go the full upgrade route, AMD 3900X + mobo would be at least $700; would I need more than 32GB DDR4 RAM for $100-ish?
So total upgrade for ~$800?

A fun thing I like to do is upgrade a system as much as possible without getting a new motherboard. Personally I'd go for the best CPU that board can handle.

M.2 NVME on a PCIe adapter works just fine, I did that myself with a cruncher. The only gotcha is that the OS has to be new enough. Original versions of Win7 does not know PCIe storage. So it needs some tinkering to manually add the drivers during the installation process. Win10 has no issues, and I assume the same for any recent version of linux.

Thanks guys! I'll go for the drop in XEON E5-1680 V2 upgrade then, and get a pci-e to M.2 adapter. Already have a nice 512GB M.2 SSD sitting here from my Dad, so may as well use it! ;)

This seems like a pretty good upgrade: https://www.ebay.com/itm/Intel-Xeon-...4AAOSwePpdyD15

Not sure how much RAM you have on those rigs... 12c/24t might require more than you have. You could go with one of these for 8c/16t: https://www.ebay.com/itm/Intel-Xeon-...0AAOSwNd5dsrAo

That's a nice chip for sure, but the multi is locked on those as far as I know. I think the E5-1680 V2 is the best one that's not locked and O/Cs well from what I could read. :)