What graphics card for the Dell Optiplex 790 MT?

Without adding anything else GT1030 is the recommended card.

https://www.dell.com/en-us/work/shop/pny-geforce-gt-1030-graphics-card-2-gb-gddr5-low-profile/apd/a9763687/graphic-video-cards

https://www.dell.com/en-us/work/shop/msi-gt-1030-2g-lp-oc-graphic-card-2-gb-gddr5-pcie-30-x16-low-profile-hdmi-displayport/apd/aa362018/graphic-video-cards

I have a Dell Optiplex 790 MT -  i7 2600 @3.4GHz with 16GB of ram.

I would like to add a graphics card but, I am having trouble figuring out which will fit physically and be compatible with the system. I am prepared to buy whatever PSU is needed.

Check out this thread:  https://www.dell.com/community/Optiplex-Desktops/790-MT-adding-PSU-graphics-card/m-p/7303338 

"790 graphics card" keyed into the Dell Community search bar also brings up more threads, but I possibly found the best one above in regards.

I currently have five Dell Optiplex 780 MT systems ea is equipped with the following upgrades.  Windows 10 Pro 64bit, Intel Core 2 Quad Q9550 CPUs, 8GB DDR3 RAM, Corsair CX450M PSUs, Samsung 860 Evo 250GB SSD drives, Noctua NF-F12 fans and MSI Geforce GTX 1060 6gb single fan graphics cards. 

Note: In order to get the GPU cards to fit I had to remove the plastic cover from the GTX 1060 cooler and reinstall the cooler without the cover attached in order for it to fit behind the CPU cooler duct and I also split the double slot cover plate so it is now a single slot cover plate.  These systems are currently mining crypto currency while only drawing around 145w at 65C. 

I was having issues with a second monitor plugged into my display port because the socket was shorting out on me until it finally died.  The addition of a new graphics card took awhile ordering online because searches pulled up low profile (LP) cards rather than small form factor (SFF). But, after returning a card ordered from Amazon, I came upon the VisionTek Radeon 7750 SFF 1GB with DVI and HDMI outputs. It was easy to add to my Optiplex 790, and I was up and running within minutes.

I have the just received the “VisionTek Radeon 7750 SFF” and installed it into one or the pie slots and I am today … I am unable  to get the monitor (tv) yo display and thing… windows 10 pro current updates as of October 2022. Question does the card have to be installed in a a specific pcie slot? when installing card and just having a vga monitor in the intel onboard graphics slot  the system recognizes the “VisionTek Radeon 7750” card a just goes to a hard halt stating there  is no monitor plugged into THE “VisionTek Radeon 7750” HDMI PORTs as it is dual hdmi port graphics card….    what is the best way to proceed?

GPU card is typically installed in blue x16 PCIe slot of 790 MT/DT/SFF which is wired x16

 The black x16 PCIe slot is wired x4.  https://i.dell.com/sites/csdocuments/Shared-Content_data-Sheets_Documents/en/us/optiplex-790-tech-guide.pdf

When you install a discrete gpu card but connect video cable to onboard video port, bios detects that as an error and prompts an error screen reminding you to change video cable to discrete card.  If no video on card, try turn off secure boot, replace cmos battery, clear cmos settings by motherboard RTCRST jumper.  Also test discrete card in another pc to confirm it works.