I've been using a flashed GTX Titan X lately on my 5,1 Mac Pro for some long-form, intensive 4K video editing and rendering using Adobe Premiere Pro cc. It's been great with no glitches (thankfully!) at all using the Nvidia web drivers and latest MacOs iterations. My system is maxed out with most upgrades you could think of for this system and handles the work impressively well. Even so, I'm still looking for ways to maximize my rendering speeds while staying on this platform. Does anyone know if a dual Quadro M4000 setup would work with the 5,1 with the webdrivers? It seems like it would, but wanted to check in with people here who may have more knowledge on the matter. I'm working on a film edit over the next year that has a lot of grades & effects. Some of my effects are super intensive, like this adaptive noise reduction that I use for some scenes that already utilizes all 12 cores and the full GPU for the render (when I applying full resources to the scene, it currently renders at about 3.29 frames/sec). I'm hoping a dual-GPU setup will help speed things up a bit more.