I have M60s, and I want to know if I connect them to two amps? One is a AV receiver for movie and the other one is a tube amp for 2-channel music. So I don't have to take banana plugs in and out when I switch between watching movie and listening to the music. I just need to turn off one amp first, and then, turn on the other one. Does this connection cause any problem?
Thanks for your advice!

If I understand you correctly, your system would look like this:

AV Receiver=======M60s=======tube amp

I wouldn't recommend doing this. Even though the amp that's not in use will be turned off, it is still part of the circuit and the amp that is on will "see" it and treat it as a load on the wire.

You might want to invest in a speaker selector box instead.

Agreed. Most amps will present some kind of load even when turned off and there is some chance you could damage the AV receiver. Go with a switch box.

Tube amps have to be always connected to some speakers when turned on. It can not be connected to a switch box. Otherwise it will burn up the tubes and destroy the output transformer. A tube amp will go into self induced oscillation and will eventually destroy itself.

Good point. Guess we're talking about a 4PDT switch box that connects each amp to a load resistor when not connected to the speaker.

Don't know if anyone sells something like that so might be a DIY affair.

Why not just run the tube amp off the pre-outs for the fronts on the reciever? That way, no switching!

Do you mean "always using the tube amp, even for HT" ? I'm guessing the problem with that is not enough power for that ungodly loud movie playing but it's a good question.

I really don't use that much more volume for movies than music, but maybe I'm atypical. Besides, it's just driving two channels.

does anyone know if they make a speaker switch box that is 2.1?

Russound Speaker Selector. Click on the "details" link for more info and a photo. Click on the "back" link for a list of more selectors.