Help choosing Power Conditioner


Completely new to this area. I would like a unit that:
a) regulates power, keeping it within the 120v range.
b) provides good and long-lasting surge protection
c) can be used with a power amp as well as preamp, and sources all together
d) Hopefully helps the audio, making it more open and dynamic without negative effects.

I need to say under about $750 used. My candidates are:
Monster HTPS7000
Monster AVS2000 (how are these two different)?
PS Audio Power Director 3.5
Blue Circle MR1200 Music Ring
Any others...
Thanks!
kck
I got a 10 amp powervar used on ebay for under 50 bucks. Has minimal transformer hum, essentially inaudible at > 3 feet away. (Did NOT purchase from Tvad!). I assume it will protect the front end pieces if lightning strikes, and that was my main reason for buying. (Also, I was able to buy a kind of cool-looking gadget-like thing that was pretty heavy, which adds to any placebo effect....so yeah, I'm happy, I think).

OK, seriously--I was unable to hear any definite sonic difference in my system, but do have a vague sense that it is probably better than just a surge protector if there's a storm, etc. Hum is inaudible at listening distance (and my hearing has been relatively recently tested and is still quite good).
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PS Audio P-300, nuff said. For source componants only. Use a PS Audio High Current Ultimate Outlet for power amps.