Power conditioners

Hi,

Need your advise on the following questions;

What is the difference between a power conditioner, power conditioner with isolated transformer, voltage stabilizer and an AC regenerator?

If I am looking at having something that will give my equipment a consistent 120v with no spikes, have a noise filter and surge protection, what brands should I look for? I saw the Powervar, the BPT and the ONEAC and they all seem different. Does one of them meet my needs?

Any advise would be greatly appreciated! My budget is around the Powervar and BPT (less than $300) and do they really improve on the sound?

Tks

HL