What GPU Should i get instead of Intergrated Graphics?

Hi, So i currently have a GTX 980 In my System but that doesnt' work in catalina so im currently using my i7's 6700k intergrated graphics

My Question is, What GPU would you recommend for catalina at 1080p? at the cheapest price.

And Would i be able to have my GTX 980 in my system, aswell as the AMD card.. for dual booting windows? And if there's any performance downsides to doing that for windows

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Thanks