Power Strip vs. Line Conditioner

A "power strip" is a glorified extension cord and in most cases junk IMHO. A very good conditioner will help considerably if your power is dirty, which is most of us. I use a Reference grade Vansevers conditioner. I has a plug-in made for amps, which sounds better than the wall in my system. Vansevers also makes a amp specific conditioner designed not to limit current (It called "The Unlimiter").
There are also products like those make by PS Audio that "regenerate" the AC power comming into your house into new fresh AC power.

There are also products like the Blue Circle BC-86 Noise Hound Power Pillow that has not plugs itself; and just plugs into a open outlet on your wall or power strip; and cleans the power for the whole circuit. I do not know how it works, but I have demo'd one and it does work.

At the risk of repeating, the above advise has been dead on in my experience. If I had a place where I could assure the quality of the power right out of the socket, that would be the way to go. However, living in a New York appartment, where the power is significantly less than stellar, I have found a power conditioner to be a good improvement for as many things as I can plug into it (I am even running a power strip off of the conditioner, and have found that preferable than running it straight out of the wall). It's not uncommon for the lights to flicker from time to time, but with a decent conditoner that gets evened out and not passed along to the equipment. True, its a bandaid where a lack of injury would be preferable--but where the injury is unavoidable it makes for a good addition.

I have a dedicated 20 amp outlet with a 14 outlet Vans Evers plugged into it. Everything is plugged into the Vans Evers, including the amp (Hafler 9505 DIABLO), powered woofer and the Acoustat interfaces. This amp sounds better this way, so one needs to experiment. Don

You really need to experiment extensively to determine the optimum for your rig, meaning different types of filters work better on different components, as was stated above. Example: the Chang series of conditioners offers various levels of analog & digital filtering, sometimes even combined into one model with multiple plugs. Yes sometimes even straight into the line is the best way to go.
What has not yet been mentioned above, & to further complicate this issue, is that various combinations of upgrade AC cords (different makes/models) work in tandem with the filtering to produce still more variable results. It can sometimes (but not always) take you a very long time to determine which combination you most prefer.