My 750 only has about an inch and a quarter above it, with front and back of cabinet wide open, and it never got over 100F or 105F when I had a thermometer in the air space above it. It has never been more than "warm" while in use. The 770, however, is heavier and will need to dump more heat out the heat sinks, so there will be differences.

------------------
gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review