One or two dedicated AC wire ?

Your attention to detail with vibration control and system layout is to be commended. 
Are you in a position to run lines to your service panel?
And what power cables and conditioner are you using?

 audiosens, you have a beautiful system and it deserves to have dedicated lines to the service panel. Your power setup has good cables and the distribution block will receive cleaner unrestricted power with dedicated lines.

I hope somebody experienced in this area chimes in, but I don’t think a tandem circuit breaker should be used in this situation.... the 2 dedicated lines would be on separate legs.

IME, audio AC lines should be on the same phase and the current draw of devices in the home  should be evenly distributed across both legs on the panel.
Unless I’m wrong, you would need to put each dedicated line on their own breaker with ground tied from the ground buss to each receptacle (not self grounded).

Luckily my electrician owned a nice audio system and made great suggestions. Instead of adding to my small circuit box with old wiring and questionable grounding, he installed a subpanel for two dedicated lines (upgradeable).
A 60A tandem breaker was used in the main panel to supply the subpanel.