Hi. First of all the RadeonProRender is free and works with most GPU's, so just download it and try it out. Simple to install, but less simple to use than Corona.
I've downloaded it and tried it, and was surprised in some regards and less convinced in others. Regarding the RadeonPro/Corona combo, then I don't think that will work out very well in reality. RadeonPro do render Corona mats, but in a "dull" and somehow reduced way, and Corona doesn't render Radeon mats at all - except for the Radeon mats build on Max's Standard materials. These are however rendered dull and reduced regarding reflections compared to how RadeonPro renders Standard mats - a thing that would be great if Corona would adapt.
That's my opinion, but as I said, download it and try it out.
Regards