Thanks for the follow-up comment on your results so far with the Extreme SST.
You will get differing opinions on the number of circuits to run. The answer will depend the power load you need to support in your listening room. Lloyd Walker and I have talked about this at some length in connection with his Velocitors and getting the best audio sound from a system. He's a believer in running everything from a single circuit if the load is OK because this often gives lower background noise in his (extensive) experience. On the flip side, many other audiophiles like to keep their digital equipment on a separate circuit from their analog equipment to minimize the high frequency has digitial can sometime intorduce along the electrical lines.
My recommendation would be to pull two circuits while you're doing this. The cost won't be much greater if the work is done at the same time, and you'll have the extra capacity if you ever need it. Then, try plugging everything into a single circuit, then balancing your gear over the two circuits, and see if you can hear a difference in the noise background. I have 5 dedicated circuits with isolated grounds and 10ga wire pulled to my audio system, but when Lloyd helped me set-up his turntable in my system, he recommended plugging as much into a single circuit as we could. He also recommended using 12ga rather than 10ga for the front end components (that don't draw a lot of current) if I ever changed anything (which I haven't). He has solid reasons for his recommendations, and I've always found it worthwhile to at least try first what he recommends.
No matter what you do, I expect you will hear a noticeable improvement with a new dedicated circuit or circuits to your system.
.
