30A dedicated line/circuit through a Topaz Ulta Contitioner (5kVA, 0.0005pf) to a subpanel. Topaz on solid stand with four soft outdoor hockey pucks underneath (variation on a Lak theme!). Sub Panel with as good copper busses as can be reasonably found. All breakers with silver plated or silver alloy contacts. All contacts treated with high silver content contact grease. Solid copper wire everywhere. Cryo'ed 10g Essex Diamond Handiwire (rec from Alan Kafton) from subpanel to the outlets. 3 separate dedicated lines. 1 each for amp, preamp and tt, and digital
all on the same phase/leg from the sub panel.
If the 5KVA transformer has dual primary and dual secondary windings I would recommend you configure the primary to be fed by 240V. Wire size minimum #10awg. Breaker size, 2 pole 30 amp.
Secondary winding configured for 120V out, not 120/240V out. (Two secondary windings paralleled). Minimum wire size from transformer to new main electrical panel #6 copper.
(New panel is not a sub panel.)
You will not need a main breaker in the new electrical panel provided you will not be installing more than 6 breakers, handles. The electrical panel will only need to be a MOL, Main Lug Only panel. 100 amp busing is plenty big.
How far will the 5KVA transformer be from the new electrical panel?
Your electrician will need to create a new AC grounded system. He will intentionally connect one of the Hot 120V secondary output legs of the transformer to earth. This grounded conductor will become the neutral conductor.
By NEC Code the earth connection shall be connected at any point on the main earth grounding electrode system of your home's main electrical service. He will not drive a new dedicated ground rod outside for the earth connection. If he does, per NEC Code, he will have to connect the new ground rod to the existing main grounding system of your home's electrical service with a minimum #6awg copper wire.... The safety equipment grounding conductor of the 240V circuit that feeds the primary winding of the transformer cannot be used for the earth connection.
As for the new electrical panel the Square D QO panel has copper plated busing. The Square D QO breakers are second to none.
If money is no object check out the Square D NQOD electrical panel board that uses QOB bolt on breakers.QOB bolt on breaker.
Note. The electrician you hire from your area will know what is required by the State and Local electrical codes for your area. For example, local code may require AFCI breakers in the new electrical panel.