Isolation Transformer and Subpanel recommendations

I currently have a 100 ft run of heavy flex conduit for my dedicated circuit;
09-11-12: Zephyr24069

If you put the new panel in the garage are you saying the new branch circuit/s run, from the new panel, would be 100' or more?

I had an electrician pull individual 5-9s copper runs for positive, negative and neutral through that new conduit 4 years ago so that part is already decided.

"5-9s copper runs for positive, negative and neutral through that new conduit" ??? 5-9s??
2) 120V circuits + 1) equipment ground?

Not sure what you mean..... More detailed info please.

There is only 1 dedicated audio system 20-amp circuit in the room. The dedicated circuit feeds a Purepower APS 2000 and distributes power to my entire system.

What is the end result you are aiming for from the new xfmr and new panel?
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End result is better quality power to my system; the dedicated circuit, rebalancing the house panel to make the dedicated circuit the first one off the main, all other high current circuits on the other leg/phase of the house panel, good quality wiring from the main panel to the room, cryo'ed Oyaide R1 outlets, etc... has taken me a certain amount of the distance but I'd like to separate from the house panel totally and improve the quality of power to the room even further.

individual copper runs pulled means individual insulated strands pulled through the flex conduit for positive, negative and neutral (ground)...

The run to the audio room would still need to be 100' as moving the panel to the garage would be a minimal change as the laundry room where the house panel is today is right next door to the garage; I might be able to save 10' or so but the difference is small by moving the panel. (The electrical main to the house itself is also right outside the garage and only about 20-25 feet from the existing house panel location.

Do you have your system posted? I'd like to see/know what you have going for power as you clearly have alot of experience in this area.

Thanks!

I would run a couple of dedicated 20A lines to the listening room, plug in a couple of Torus or Equi=Tech balanced power units and be done with it. I run my main system off a single 20A line, feeding three balanced isolation transformers mounted in a single large chassis, which sits near the bottom of my equipment rack. Each transformer feeds its own Oyaide R-1 duplex outlet. It is like having each component on its own dedicated line. Simple and uncomplicated, yet effective. I've been running this kind of setup for 8+ years now.

Gbart....thank you very much! If memory services the Torus units have their own isolation transformers built into them so this would accomplish more than one goal at the same time. Equitech also makes a high grade all in one panel that has an isolation transformer, EMI/RFI filtering and an isolation transformer all in the same unit; don't know what this costs but it seems like there are several ways to accomplish all this that people have utilized with great success.

BTW...in talking with an audiophile who knows a hell of a lot more than I do on this, it became clear that some of my responses and my not being an electrician have caused confusion on the thread. Apologies all around for this...
Thanks to all of you who tried to help. I've pieced together (with Arnie's help) the essential points I should be chasing if I make this modification and definitely appreciate the help!