Sierra GM 14'2 Haswell Defninition GTX 750 Ti... all 3 monitors up with Video but alas no HDMI Audio.... I reckon this is an nVidia Driver issue... whatever this patched driver is doing it certainly does give Graphics acceleration but the HDMI audio is broken. Will have to wait for first "official" Sierra driver. I had a few issues,,, I had to nuke an updated PB I had and reinstall PB 7 before I got any acceleration at all... and then it was only on 2 monitors.... but after 2 reboots the straight HDMI to my Samsung TV worked ... Not sure about anyone else but I still find Sierra buggy. I have big issues trying to mount Efi Volumes. If I use configurator it does nothing... or opens an empty Efi folder rather than my boot volume... With terminal I get a not found... but using the two together I somehow eventually get there... Other installers simply don't launch at all or return code messages...