Is a Dual R9 280x sapphire in Crossfire config the best deal for Video editing on a Mac? These can be purchased used for as little as $300 for the pair. Is this the best config for a hack? Does the R9 280x work vanilla on OS-X Is a Dual 280x build better than a GTX-980, GTX-1070, or GTX-1080 ? I want to run dual 4k displays?