Hey Kat, thanks for the really informative posts on this subject, its definitely been a great source of information.
I have the same machine, Elitedesk USDT, that I wanted to use for a Kodi media player, streaming and playing local files - 4k UHD movies, flac files etc, no gaming, but found the configuration I had - i5 4570 with 16gb RAM - just didn't cut it with 4k UHD movies - stuttering, lag etc - so figured a graphics upgrade was needed.
I tried -
HP Nvidia Quadro K1100M - no dice, wouldn't boot. No error codes or beeps, just sat there, possibly hanging on the POST screen but no display to try and troubleshoot
Nvidia Quadro 1000M - lots of beeping, not booting. Possibly mismatched Dell board - ?
Finally got an AMD Radeon 7650A to boot and run.
This played 4k UHD movies smoothly but boy did it overheat.
The card didn't come with a heatsink so had to get creative. Used a cut down heatsink and small fan from an old Radeon PCIe GPU hooked up to the SATA power connector next to the MXM slot, some thermal pads and zip ties (no mounting bracket with the 7650A) and that solved the overheating issues. Pic attached to show the installation. Wouldn't have done this without the inspiration and ideas from this thread so thakns again!
Peace, Topher