Graphics Card Boot Up Screen?

I recently bought a Gtx 1060 for bootcamp unknowingly that it wouldn't show the boot up screen on my 2010 Mac Pro. It originally had two Radeon 5770 HD's but those are no longer available. The computer is currently stuck on the boot camp os not able to switch back to the mac os without the boot up screen. I was wondering if any could tell me a cheap medium quality graphics card that will show the boot up screen? Also would I be able to keep both of my graphics cards in and it would still show the boot up screen? Thanks.