Now with new CPU WUs there is an ever increasing reason for more CPU throughput. Are CPU expansion cards at all realistic or even consumer ready? I love GPUs due to their integrated memory on a separate card with no need for an additional case, power supply and cooler as it comes included.

I know these exist for servers but perhaps we could multiply the CPU capabilities of our volunteers by having an expansion card solution?

It might exist but I've never heard of an add-in CPU for anything but servers that were designed to have multiple CPU/Memory cards.

Ryzen for cheap cores with a 1700 or one can try to get many cores with used Xeons off eBay. Those are probably the best bets at getting CPU power for reasonable prices.

One of the bigger costs these days will be DRAM. It's nice to have 1-2 GB per core as some projects can use 1GB per task. I bought a combo package from Natex.us with CPU/Mobo/Mem and the price has nearly doubled for the same equipment.

The nearest might be the Intel Xeon Phi multi-x86 coprocessor. But I've never heard of anyone even attempting to to write the scheduler hooks into BOINC.