Dedicated Electrical

Everything feeds crap back into the line. DACs and other digital gear with high frequency chips are probably much worse than subs. In general though it is fruitless to point fingers power is dirty, and more things being plugged in only makes things worse. 

There is a clear distinction between hearing and listening. What you just described 

I may not immediately hear something, but it can sound better without me immediately knowing it, except, over a period of time, I begin to realize that I am more gratified than I was in the past

is the result of a process that can be learned, practiced, and improved, just the same as any other skill. You will want to search my name and read about it. Coming soon!

First rule of audio, if you don’t hear any difference, don’t worry. My rule anyway, if I don’t hear it, why bother? So it seems to me you already have a power strip, in this case one called "Prometheus Power Flo" and so you might as well use it.

That said, there is a way to determine for yourself whether it "works" or not. Start by plugging everything into it and listening to your system that way. Do this long enough to get used to the way this sounds. Then unplug one component and plug it directly into the same outlet as the conditioner. This avoids potential differences between outlets, possibility of ground loop noise, etc. This is a true test because the only variable is the conditioner.

Hopefully you prefer the conditioner. But if not then use the same process to find a power strip.

Don’t worry if you don’t hear any difference. In this case there are two ways to go. One, you remain happy as a clam, content in being satisfied with whatever you have. Two, this bugs you and you want to find out whether your lack of hearing any difference is based in reality, or a lack of listening skill.

I know which one it is, but remain agnostic on which choice you make. For the simple reason this is all about building a system you enjoy. Not me. Not anyone else. Just you. If I can help you be happy with what you have, that is just as gratifying to me as if I can help you learn to master all the many ways you can make it better, and appreciate it for being better.

To that end I will soon be writing a series of articles on how to listen, critically and effectively. How to evaluate what you are hearing, with the words to describe and talk about this with others. And best of all, how to develop the ability to do this with aspects of sound you are not currently aware of or able to identify.

Immathewj, power conditioners used to be all over the map but today are like most things more consistently good. Even so they are like all components very individual and to be judged on that basis. The way I see it there are so many areas of improvement it is just as good to do fuses, springs and so on first and leave conditioner for later as the other way around. As long as you are putting one foot in front of the other and not sitting still you are making progress and that’s what counts not any one particular thing. 
The conditioner test is on my (very) long list of ideas to try when I can find the time. In my system a step down transformer goes from 240 to 120 and then another one is in the conditioner. All of this can be changed to compare, but being hard wired is a bit of a project, not like most things people would just plug and unplug. 
Many years ago I had some Electraglide power cords and learned that they were not earth ground. They looked like they were, they had three prong connections at both ends, but they weren’t. The dealer told me they did this because it sounds better. This was at least 30 years ago. Then at Chuxpona21 (do a system page search) Silversmith owner Jeff Smith was here. He thinks so much of floating ground he carries a cheater plug around in his pocket, eager to prove how much better it sounds. This is a guy who designs cables for a living. So I am not surprised if some of what you have was made that way as part of intentional design. 
 

immathewj- Your old vintage components are made that way because that’s the way pretty much everything was made back then. That’s the way the US electrical grid was designed to be run. Over the years though people get less and less educated, more and more heavily regulated, until today we are afraid of our own shadow. Redundant earth ground is now code in most places, and some are starting to add an even more redundant third ground to plumbing. When we see people attaching copper ground wires to plastic pipes we will know we are at Spinal Tap 11.

Eliminating, cutting, or "floating" the redundant third earth ground is one way of solving ground loop hum problems. In your case, with older gear with just two prong AC you already are "floating" the ground.

Power conditioners, almost all of them, primarily use a large transformer. These transformers are designed to be very efficient at 6oHz. AC is 60Hz. Ever notice makers of tube amps and other things like to brag about their custom wound transformers with great top end frequency response? Because it is hard to make a transformer do high frequency. Radio frequency is in mHz- mega. Not kilo, mega. So AC coming into the primary is chock full of RFI, but the AC coming out the secondary has a lot less. This is pretty much a power conditioner in a nutshell.

There is no "isolated" with running lines. Everything plugged into the outlet is connected to everything everywhere else plugged into the grid. All you have to do is follow the wires back to the panel, remove the cover and have a look inside to see that this is the case. Everyone else’s home is wired just the same. All those wires connect to neutral, and they all go back to the incoming utility. Everything is connected to everything else.

The only true isolation is a battery disconnected from AC and housed along with the component in a shielded chassis. I have this with my Rens Heijnis modified Strain Gauge phono stage. It works pretty good.

See my simple test above. Turning off two of your circuits will disconnect those two hot leads, reducing by that much the length of wire collecting and funneling RFI into your system. To that degree it will help. You might even be able to hear it. I have done a similar test, turning off some breakers and then others, and there is a difference. The more the better. Just remember to turn them back on. People get so cranky when the hot water runs out.

That's right. All wires pick up RFI. Just what they do. Look- what's an antenna? Nothing more than a piece of wire. The wire is cut to length and laid in shapes or patterns to maximize particular frequencies of interest, but basically it is just a wire.

Radio frequencies are everywhere. We get our power from wires. Therefore, all of us have RFI. All we can do is take steps to minimize its impact.

A simple test, turn off as many breakers as you can, and you will hear the impact of reduced RFI. It will sound like you just put your system on battery power. Which I know what that sounds like from modifying things from wall AC to battery DC.

Experience gained with hands-on testing such as this is how I know a sub panel is sure to add unnecessary expense and noise, and the same goes for multiple lines.

Excellent choice.

Adding another panel adds additional connections, another expensive panel, and an additional circuit breaker. The only advantage would be if the wire run is very long, 100 ft or more, in which case it would allow use of much larger gauge wire for the majority of the run with the panel located near the system. Any other situation and it is worse not better. 
 

Muliple lines runs the risk of ground loops. Even if this is avoided every wire is an antenna bringing RFI into the system. So one single dedicated line is the way to go. 
See Michael Fremer talking about his system when he says the same thing. Years ago. People are slow to adopt new information.