Can anyone confirm the rumor that El Capitan has brought back support for more than 2 GPU's? I'm currently running windows 10 on a supermicro 7047 with 1xK4200 for GUI, and 5x K5200 for CUDA (one in the box and four in a cubix elite). The quicktime (especially prores) support in the windows version of resolve has really been getting me down. I heard that El Capitan can support more than 2 GPU's again. If this is true, it may make sense to build a new hackintosh to replace this supermicro and potentially switch from the 5x K5200's to say 4x Titan-X's.
I should be more specific about my issues with quicktime on windows resolve... We have found the YUV flavors of prores (LT, 422, 422HQ, etc) to be very unstable. We have also found general system performance to be very poor with high resolution Prores4x4 as compared to the same material on a mac. The complete lack of support for XQ is also a drag on our workflow when dealing with lots of alexa footage.
ProRes YUV has always been flakey. I would recommend always using ProRes 444 (or a variant) when possible.
I can't help you with running ProRes on Windows. I think there are issues between the OS, Apple, and BMD, and you could chase your tail forever trying to put out those fires. My only advice would be to convert everything to something more Windows-friendly, like DHxHD or DNxHR. Either that or go to the Linux version, which is not cheap but does work well.