I just came across a "heat" issue with the SRM450 and thought I'd share it. It seems that they automatically shut down at 113 degrees. Since the amp is built into the speaker cab a shutdown could happen if the speakers on on the floor when playing in rooms saturated with body heat (I've been in some pretty "hot" rooms). Here's the URL on the discussion = http://www.live-audio.com/messages/56079.html

Don't know if this has happened to any other SRM450 owners but its good to know about before buying them . . .