Most, if not all, power conditioners won't help with noise floor, but the reviews of some of the balanced power units said that they did. I'll have to track one down, but these were legit reviews for studio equipment, not home use so those guys are way more picky than most of us are. Plus, I seem to remember the monitors used were quite expensive. We're probably talking about the absolute last thing you can do to eek that extra 1% out of your system.
I'll admit, if I had the cash, I'd try one if I had higher end equipment. Mine wouldn't really benefit from something like that.
The marketing for most of the power conditioners is that they "clean" the power coming from the wall before it gets to your equipment. The thing is, the power supply in the equipment is already doing that to an extant, so what's the point? That, and the voltage regulation from a UPS that produces a "pure sine wave" is supposed to be as good as it gets. Tons of UPS have this feature and aren't expensive, but won't change anything about the way things sound.
Someone like
@PENG or
@TLS Guy can explain it better than I, but the general consensus is that power conditioners aren't going to do much to "help" your sound save for very specific circumstances.