I have some "cloud" servers at home DELL C6100 .. Xeon, lots of RAM. I used them as a lab at one point but am now confused what to do with 'em. These days, I am playing with deep learning. Is it reasonable to pick up some cheap GPU to go into these? Any other ideas?
Does your GPU fit that chassis? That is my major concern with that. Beyond that, the major weakness of those chassis is that they eat a bunch of power compared to modern processors. That's why they're being sold off.
Other than that, the default GPGPU picks are either the OG GTX Titan or the 780 Ti since either has the same processor as the Tesla compute cards.