I have an HD 7970 (AMD) and a first gen TITAN (Nvidia). I *think* they both work, but haven't run them in a year or more. The 7970 should be really good with Einstein and MilkyWay. The TITAN should be good with double precision Nvidia projects like GPUGRID, I think.

If you will use them for crunching for the team, they are free.

For MacOS users, they do NOT work as eGPUs with Big Sur.