What I have found with Home Audio forums is they are very clique oriented.
AVS is annoying with all the HT Onkyo, Denon, Paradigm, Klipsch, HTIB etc etc guys.
Home Theater Shack, is meh on a lot of things and I really don't check their anymore.
DiyAudio is alright, if you can dig through all the bad ideas to find the good ones. It is a great place to ask if you have a specific circuit question or need knowledge about something very specific electronics related.
DIY Home Audio, I think I'm the only person that checks that forum.
CA.com Home Audio section, a bunch of yahoos asking about putting car amps in their house even though there have been a 1,000,000 threads on it already. Plus you ahve the hanyacks like Megalomaniac who just cause trouble. (BTW it takes 5 yahoos to equal 1 Hanyack; these are actual terms I use in daily life.) ((BTW J/K Megalo don't want you getting butt hurt or anything.)
Home Theater Guild (HTGuide) - If you don't like B&W, Classe, Rotel you probably should look for another forum. There are a lot of guys who like Emotiva, Parasound, and a few others. But, mainly that is a B&W forum with some nice DIY stuff also found there.
I could continue. Basically you should find a Magnepan forum, but I don't know of any. Maybe Jim does?