I have a similar system (running SL 10.6.8 for a year now, with everything working except for HDMI Audio) and I'm also curious if my system is supported by ML.
Motherboard:
Gigabyte GA-P55A-UD3
Processor
Intel Core I7 860
Graphics Card
Club3D HD5770 (CGAX-57724I)
Could anyone give us some advice?