What's ironic is to talk about distortion from power conditioners, but everyone is using gear without low distortion. Power conditioners have very little effect on THD. But there is a type of distortion that no one is referencing to because people aren't so clear on what's going on - they may be hearing it but describing it as other things. I hesitate to call it distortion because it isn't an apt description when referring to AC where everything is, eh, a bit loose on the quality of signal. None the less there is often "linear distortion" occurring. Most will refer to it as "current restriction" if what they are describing is actually even related to power quantity. It tends to soften from somewhere in the mids, to the highs, and overall presentation a bit. Sometimes it happens during transients only. You might hear it in the bass but actually this is typically very rare to be perceptive of it. What is occurring is saturation of certain parts of the device (if it's the guilt of a power device). When saturation occurs from the amount of current flowing, it is the voltage that takes a hit. That's more problematic than maybe it sounds, given that current and voltage already tend to be a little out of phase on our power (power factor). What isn't happening is current reduction (the physics of current reduction aren't really in the realm of audio products until something literally burns through and severs the connection entirely). This is all, of course, barring the your amplifier isn't clipping (soft clip, not the hard one you noticed big time).
Ground, safety ground, is not a drain. Fundamentally it's important to know that electrons flow toward hot, towards positive. So you can't just "dump" everything off onto something, because the absolute fundamental first most basic thing about electricity makes it impossible. Ground in general is one of the most complicated subjects there is... it cannot be as simple as Roger is implying. Star grounding is a simple way to try and solve problems but ultimately isn't the final word. Things are more complicated than that, and real engineering knows that. I don't believe at all that you can "solve everything" by grounding because it doesn't address ten zillion things like PSRR and sooooooooooooooooooooooooooooooooooo much more. There's a lot of engineers that design some pretty great circuits and still don't full get some grounding problems in some cases. The likelihood that just any pedestrian off the street can solve their situations by saying "star ground" is basically zero.
Ground with more resistance sound better? That's actually entirely plausible because resistance contrary to popular belief isn't necessarily bad in the least, but rather not a very economical way of dealing with anything. Resistance burns off lots of power, that's the biggest problem with it. But it can also dampen certain things, including a lot of noisy trash on ground that is in frequency ranges that don't play by your ordinary rules and tends to be rather devious.
What's funny here is I agree that most powercords and things don't work well, they don't sound right. However I strongly encourage power conditioning. What conditioning? Now that's a very challenging question. I like my own the most and there isn't a commercial version yet. So it's very hard to recommend something. If you have disastrously bad power you might as well get anything that will fix it. I can say this, the regenerators disturb me a little in that the powercord going into them has a massive effect on sound...
Trying to pick out why you hear everything you do when you start using power conditioning is rather hard. They do often reveal other flaws in a stereo. They may thoroughly open up your stereo to sounding like that one note wonder you get from lots of estranged cords and other things. But you also potentially run into other problems like incompatibility with devices. I would venture to say that's a major contribution to DDK's findings. I say this because maybe he isn't thinking about, but does know... Lamm uses a "widget" on the input of their ML3 PSU (and probably others). These filters don't necessarily play very nicely with other things all the time. I'm not a fan, but I believe they're using ones that are mil-spec because the average IEC filter is absolute garbage - and the mil-specs are decent.
Different people balance the sound of systems differently. So the variables involved are almost endless in some regards. Some may like the sound of what the naked AC sounds like. I think it's the fastest way to fatigue... but others will call the attributes dynamic. When you have better quality AC you often find out that albums are a little different than you may have previously believed. I would say an incorrect way to judge them is say with a single album because if you were getting closer to the real sound of the album, you could misjudge the characteristics of the album as the characteristics of the change in AC power. But that's what I see people doing all day long. And I'm 100% sure that some people just don't hear fatiguing attributes like I do - to them it is not -, and I think for some it's age related.
There's nothing wrong with just not using any of it. It's subjective. But IMO you can't get the quality of music possible without conditioning. The percents detected on the line aren't important, the sound you hear is what matters and even people with 3% have found drastic improvements. Our gear can often share noise with other gear, too. There's an awful lot of variables and that's the same reason why most companies get power conditioning utterly wrong. It probably sounds like I'm rejecting it and praising it at the same time, I am. That's why I had to invent my own stuff.