Wire the House A/C or get Power Conditioner?

Agree you should use 10ga wire, and yes some electricians may grumble a bit.

As to installing isolated ground circuits and receptacles, I've become convinced that in residential construction with wood stud walls, or solid masonry, isolated grounds do not add any benefit.

Isolated grounds are used in commercial construction because of the metal studs in all the walls makes the entire structure one big grounding grid with lots of potential for adding multiple ground loops and noise.

This is simply not an issue with outlet boxes nailed to wood studs. In the residential construction setting, the single home run pull of cable back to the circuit panel makes for a single "isolated" ground wire connection. (But if your walls are built with metal studs, by all means use an isolated ground wiring installation and receptacles.)
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Power conditioner first;the amount of money involved will be far less than dedicated lines. If whatever problem you think you have is still audible, take the next step. I think it is odd not so long ago "ultra" cables,cleanpower,outlets,power cords, etc. were never a concern. Input, amplification, speakers were it. Once the basics are covered, someone somewhere will tell you about a problem you didn't know you had and offer a solution to your newly revealed system flaw. Spend as much as you want, convince yourself that it makes an audible improvement. Good Luck. I'm spending my money on music.

Rushton;
Interesting view on isolated grounds . Your method may be less involved .

How would you address the noise/interference issue , transmitted through the lines , from things like digital equipment , electric motors and flourecent lighting ?
I don't understand how you are 'isolating' the dedicated lines from the rest of the household system if you are connecting everything to the same ground .

Oh , and a happy electrcian often does better & 'more' work than an aggravated one ! And may charge less !

However , I will admit to running my lines with 10g. wire , which did receive a comment !
But I also fished all of that wire from the panel to the box's and pounded the ground rod , in the middle of a Florida summer !

No flames , just knowledge .

what's the best bang for buck power conditioner? PS audio?

I like the APC s15 or s20. PS Audio's are great too, but don't have the batter back up.