Anybody know of a web place to go for reliable avionics installation chat? For my example, I want to discuss connecting a KX-155 audio output signal pair to a single-ended audio panel.

Two good sources of info/discussion are Cessna Pilot Association( $55 a year) and Cessna Pilots Society (free)...google them...both are visited by many of the same people and both are an excellent source of technical info. CPA will get you more technical discussions while CPS is more of a "community" type site. The $55 a year I pay for CPA saves me thousands every year and has for the 12 years I've been a member.. Post your question there and I'll almost guarantee you 10 replies in 24 hours....

CPA www.cessna.org
CPS www.cessna-pilots.net