Best buy and the rest of the retailers never want to explain properly about buying a 5×1, 7×1 or other tuner because you would never buy a system from them.
the facts:
A 5×1 home theater tuner means that you can hook up 5 (8 ohm) speakers to the system and nothing more unless they have a connect tor on the back of the unit that allows for an external amplifier to be attached.
A 7×1 means the same but allows for seven speakers.
If you want to use your system for both home theater and a music and sound system for your house, you need to buy a am/ fm tuner
that has:
1. two zones that operate independently
2. an amplifier pre out that allows the unit to be hooked up to an external amplifier.
3. an amplifier that has enough wattage (power) to run all the speakers you have in the house for music and sound.
4. volume controls that allow for matching the speakers to the tuner or amplifier.
If you presently have a home theater system in place, and the unit shuts down when you turn the volume up, your unit has self protect and is shutting down to protect itself .
so as you can see it takes a professional to install a real home theater system and music and sound system, or you have to do a lot of reading and need to learn a little electronics
sparky bob