Yes, you can but it won't increase dramatically as it was old and you have to play around with the settings to get max out of it.

Quadro M4000 SLI? Well, it has to depend whether your motherboard can support or not. If you're using Quadro M4000 mean your motherboard should be 2015 or older, which most of them might not support for SLI. Entry level motherboard don't support SLI too. Is depend on how you going to use it if you plan to go for SLI. I know Nvidia graphic cards can support SLI but not sure of AMD Quadro M4000. But if you plan to use SLI to play modern/latest game with Quadro M4000(with 144Hz and 4k or 8k), simply forget it. Old game yes you can. With SLI, you can get 4k or 8k with higher frame rate than single piece graphic card.

If you want to use SLI and run cryto-mining, it definitely give you the best result. So is running AutoCAD or Autodesk 3D Studio Max/3DX.