The GPU's I see available for the R720 is the Nvidia K2000, K20, M2070Q, M2075, and K40M. As well as the AMD Firepro S7000 and Firepro V7800P.   Hope this helps.
I recently purchased a R720. When I load a Linux (Debian) OS with a GUI i end up with a display that is blue with lines running horizontal across the screen dividing the screen into several segments. Other than occurring GUI the unit seems fine, I say seems as I have not been able to get past this stage. I have put non GUI Debian on the server and it seemed to run the OS fine. Is this a fault with the system or is it not able to display a GUI OS? I am really hoping to have a GUI to work with whilst I setup and configure the server, do I need to put a GPU in the server to resolve this or what? I am a tad new to this and am trying to learn more on servers and networking hence the purchase so any help would be appreciated.
R720 Graphics corruption