I own a APC S20 with battery back up. I don't notice any limiting of dynamics. I actually love the unit. I think it smokes the Hydra 8 that did indeed limit dynamics in my system.
I own the APC H15. No problems. I find it usually delivers around an average of 3 amps... or about 30% of available (rated) continuous power. ( I think it wise to go oversized for a power conditioner/stabilizer and one that APC claims to have thoroughly tested to be capable of delivering high peak current with demanding power amps). The APC H15 has dedicated sockets for a power amp and sub. Although I use both plugs for main speakers only and just plug my sub directly into a wall outlet (if anything the sub is likely the biggest transient power hog and least sensitive to HF noise...so to me it seems logical that it goes straight into a wall outlet and no power bar of course).
I suspect that systematic problems of dynamics with several Power conditioners probably says more about the power amp power supply (poor design) than all these "bad" Power Conditioners (how can all conditoners be BAD - unless you are consistently selecting something way to small for the task at hand). Nevertheless Bryston, a respected power amp maker, says NO to any power conditioners. So I think it best to follow the manufacturers recommendations, which I do for the Bryston driving my surrounds.
Does the APC H15 make an audible difference - no effect on the sound of the powered speakers, at least as far as I can tell (switching between direct wall outlet and APC H15). But then again I am a skeptic...and a difference must be possible to detect using A/B blind comparisons for me to accept it.
I do find the APC H15 helps the DSP pre-amp slightly...perhaps some low power digital devices (with poorly designed power supplies) are most susceptible to noise from dirty power or this is just a freak thing. I have a very cheap PC plugged into the same set of wall outlets which might be the cause. All the same, I was not impressed that my Anthem AVM 20 sounded slightly different and regard this as a failing of the Anthem AVM 20 power supply design, obviously not as robust as it could be. (For perspective, my CD player and DVD players seem totally unaffected by where they are plugged in).
To me the APC H15 is a mundane addition that probably yields much more in terms of safety than anything else...surge protection and more. Who can say if it will work with other power amps and not limit dynamics....APC claims they have tested the APC H15 with power amps...and they do have UL certifications on their products and are used by large corporations to power computer databases globally (i.e. no fly by night small corporation making production runs of only a few hundred units...i.e. deep pockets and deep liabilities...so high probability of serious engineering) Nevertheless, I can't promise it will work for you but my experience suggests it might.
Frankly I don't like power bars all over the place (on carpets, inside cabinets, or squeezed behind cabinets).....especially the plastic kind! I worry that one day something may fail, a breaker might not trip, and a faulty power bar melts and causes a fire. So I really like the fact that the APC H15 power conditioner/stabilizer sits in a metal cage, which is intrinsically MUCH safer than a power bar. To me this is ACTUALLY the most important feature. (Power bars stuffed behind components in cabinets being, IMHO, a possible safety hazard)
