I recently found an AG500 in killer shape here locally and it's a great amp !! I do have a question about the channel switching. I notice even with the volumes all the way down that when you switch the channels with the front panel switch, you get a rather heavy bump (not a pop) out of the speaker. I notice the speaker moves quite a bit when this happens. Aggie says this is regular. I believe them but just wanted to make sure everyone's AG500's are doing this and therefore is normal operation. Thanks in advance for your help folks !!