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'm a fan of the balanced power units which include the likes of equi=tech, exactpower, bpt, blue circle and others. Equi=tech has a terrific reputation and has been doing balanced power the longest, particularly with major recording studios. However, bang-for-the-buck goes to Blue Circle for its MR1200. I use this unit and have experienced enhanced low level resolution and quieter background; however, don't expect sonic improvements because this is extremely system/environment dependent. I demo'd another power unit that, beyond peace of mind, made no audible difference. I would not recommend the smaller BC mr800 as it might compress dynamics of your amp. Of course the other route to take is to install dedicated ac lines, a wholehouse surge at the breaker box, plug your amp directly into the wall and your sources into a hydra 2 or audio magic mini stealth. Options, options...fun hobby huh?
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I will also suggest looking at some of the BPT options that may be a stretch on the old budget.

And for what it is worth, I agree that dealers or even members that may be listing something should disclose that fact and only be responding if they can be adding something useful other then an advertisement to the discourse.
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I'll second those Powervar and Oneac units. They do what they're supposed to, are well engineered with quality components. I'd put them up against the audiophile grade conditioners at a multiple of their cost here and on Ebay.