You should be good I think, if you have any issues just get an i3 4130, remove the gtx 1050 ti, install windows 8.1 install the A18 bios update and then reinstall the i7 4790 and gtx 1050 ti, then reinstall windows, please accept this as solution if it is useful
I just purchased the last part of my custom dell 9020 build which was the i7 4790, I also decided to use a gtx 1050 ti for the gpu, I purchased the motherboard brand new so I am assuming it has the earliest bios update and I am a bit worried about the bios being too old for the hardware and I am in a state of confusion on what to do 
Optiplex 9020 BIOS