Davinci Resolve 9 together with a Nvidia GT 120 & GTX 670

Hello Blackmagic Friends!

I´m just upgrading my Mac Pro in order to get the best out of Davinci! I just love that program.

But now I´m having this weird issue.
I bought the GTX 670 and wanted to use it in conjuntion with the GT 120 as the GUI Only Card.
Now everytime I start Davinci, it complains that my Hardware is not as it should be... and if I look under "System Overview" Davinci states, that my GTX 670 is used as GUI only & the GT 120 is the Video Card 2.
I´ve tried to swap the PCI Slots of the two cards from Slot 1 to 2, but it just keeps complaining, doesn´t matter where I put the cards.

What am I doing wrong?
Any ideas?

put MONITOR to GT120 and get out monitors from GTX670 ..

Don't connect any display to the GTX670. Only connect the display to the GT120.

Resolve will then use the GT120 for GUI and the GTX670 for GPU.

Thank You!! That worked!