Isolation transformers are best used on source equipment....and most benefit
generally realized on digital gear. Ie, I haven't found much of any benefit on my turntable(s), for instance.
The lower the noise in the line going in, but maybe more importantly, they act as a wastegate from allowing digital garbage back into the line (and your system)
Your gonna' get different opinions of the level of power conditioning needed in this circle....but, my opinion is it's best to get a few
smaller Oneac or similar IsoTrannies and isolate each of your digital items.
Your DAC functions as your preamp and it's tube....so it
may require a larger IsoTranny on the order of the PowerVar (as would your Hitachi TV if you want to put that on there, too)
Leave the subwoofer and McCormack amp straight into the Naim/Wiremold power strip...their power draw will likely starve these components if even a HUGE IsoTranny is used. The resultant sound of starvation is troubling to my ears...but not everyone hears it.
I use the Adept stuff for my amplification equipment and it seems to help a bit with higher fidelity with the starvation caused by use with an IsoTranny (or in my case the use of two different brands of very high capacity, expensive, Balanced Power units)
I haven't found the justification of buying a (most often) Balanced Power unit over a (often much less expensive) medical grade Isolation Transformer to be there, myself.
Different strokes for different folks, of course

John