FURMAN, PS AUDIO, ISOTEK??

I'd go with Isotek - I'm biased since I own a Mini-Sub II. PS Audio units are are energy wasters with mediocre performance. Stay far far away from Equi-Tech products,they sound closed-in, and have a horrible build quality. My equi-tech had "reset" issues, and when I took the top cover off, I was amazed at the sloppy workmanship there was - and at the amount of aluminum shavings that where inside the unit. Buy an Iso-Tek or Transparent Audio unit, and don't look back, just enjoy your music knowing you've got a REALLY quiet background, and are using "protection." All the best. - Sorry that I haven't heard Furmans.

The Furman is a good unit as long as it is not overloaded. It is used a lot where AC voltage is variable, as it will try to keep the line voltage stable (it has a circuit for switching taps on its isolation transformer).

It is most often used in studios. As I mentioned before though, you do not want to push it hard. I would not use it with a power amplifier unless its a small transistor unit.

None of the above. Start with noise-filtering power cords by LessLoss (DFPC Original or Signature; $595 and $1149 ea., respectively). There's no risk of inhibiting dynamic performance with these power filtering power devices, and their multitudinous benefits are immediately obvious. Once hooked on those, you might consider the LessLoss Firewall power conditioner. That's some serious performance enhancement. I own all three of these products (3 Signatures, 2 Originals, and 1 Firewall) -- so I'm speaking from my own experience here.