CyberWalrus, the first DSDT edit you did for me seems to be on the right track. (For the 2012 VAIO SVS)
On Lion,
with GraphicsEnabler=Yes, instead of a black screen, now I get a gray screen on my laptop's display. When I plug in a HDMI external monitor, it displays what looks like an "extended desktop" with the galaxy background, but it's missing the dock and the menu bar at the top. The laptop's display then turns black, and unplugging the HMDI cable doesn't bring back the display on the laptop.
On Mountain Lion,
It displays a garbled (corrupted) screen on the laptop's display, plugging an HDMI monitor causes the laptop display to go black, while displaying a gray screen on the HDMI monitor. (GraphicsEnabler=yes, -x) Mountain Lion won't boot up without -x.
CyberWalrus, I've uploaded my DSDT and EDID again (with Stamina, speed mode this time). Would you be able to edit again my DSDT for me? (to add my EDID info to it)