Sharing a subwoofer with 2CH and HTs rigs!

Mesch- I certainly don’t need to have both amplifiers on, and don’t plan on it. My worry is that, by accident, at some point I WILL, and want to avoid that possibility! 

I’m also pretty sure most of the big box places like Best Buy do set-ups like this in their auditon rooms. I just want to be 100% sure as I really like this Velodyne sub and they’re not easy to find anymore.

Flynnrd, I understand. 

I had use a Niles SAS-1 as a switcher to select output between a AVR sub-out and a active low pass xover from a two channel preamp to a subwoofer via RCA cable without any problem. Actually, any line level source switcher/selector can get the job done, and I believe if both source are turned on will not causing any problem as long as only one source is selected and connect to the sub input.
The only possible problem I can think of is most of the RCA switcher/selector only switching "+" side and the ground connection remain connected. In some cases, it will introduce ground loop hum. The solution is modify a xlr switcher to rca so both "+" and ground connection can be switched on or off.
Another possible problem is "cross-talk", it can be overcome by simply turn off the unwanted source.

Thanks everyone. A sound engineer I know thinks it won’t be a problem. I’ll be trying it later today and will post the results in case anyone else is interested. I searched everywhere I could think of on the internet and couldn’t find anything!