What is the best GPU for a Dell Optiplex 780?



It wont support a 1030 as you will need a system with a UEFI BIOS, and none of the Core 2 systems had those. You will need something before the 700 series from Nvidia.
 

Eximo

Titan
Ambassador
Depends on how much money you've got really, and the vital stats of that particular 780. Very optional those models. Power supply and physical size being the two largest factors aside from price.

A GT1030 should work though. You may need to preemptively update the motherboard BIOS from Dell's support site. Though given the variety of motherboards available in that model, there is no absolute guarantee.
 

Eximo

Titan
Ambassador
I believe we had reports of success a few days back, let me see if I can find it.

https://www.youtube.com/watch?v=mHTMZHcFaJE&list=WL&index=1&t=86s

http://www.tomshardware.com/answers/id-3520508/1030-low-profile-bios.html

Found one on Youtube with a GTX1050Ti in it playing GTA 5 with a Core 2 Quad as well.
https://www.youtube.com/watch?v=7TFfNredw0U

No absolute guarantee and I would normally exercise caution, but it looks like Pascal will at least work with an already built 780. Not sure if you could install Windows with it or anything. Just make sure you can return the card in case it doesn't work.