graphics cards for Resolve

I was wondering if anyone could help me with a graphics card solution under $100 US that will handle Resolve? I have a Mac Pro tower but the Radeon graphics card that is in there won't handle Resolve. Anything from Best Buy that will suffice?

Is this a trick question?
Please read the specs at support site

I don't know of anything for under $100, but my ati radeon hd 5770 1 gb seems to work adequately. Pretty slow, but it does work.