An unconventional approach to POWER MANAGEMENT

I am an Electrical/Electronics Engineer with experience in analog/digital design, amplifier design, computer design and also a state registered power engineer.

So, yes, I'm one of those.  Rattling of code is not a negative.  people that ignore local building codes are just stupid. Sorry, I can't be more polite.  These are people that do what they "think" instead of realizing that the codes are there for pretty important reasons.

That said, my house is on a raised foundation with a crawl space that when I was younger, wasn't a problem.  Now, it sucks having to crawl under my house to repair plumbing, wiring , etc.  But, oh well.

years ago, i installed four (yes four) dedicated circuits from the panel to my listening room.  One for each amp (I have three).  two mono amps, one for each lower bass panel on my Martin Logan Monolith III speakers and a stereo amp for upper panels.   The other outlet is for a really nice power conditioner where all the low level electronics (pre-amp, phono  stage, turn table power supply, electronic crossover, music server, cd transport, DAC, etc.) are plugged into.  No noise!  ground floor .....  it worked very well for me.    Of course to me a dedicated line means that the hot, neutral and ground all go back to the panel and are not shared with any other circuit.

With a crawl space instead of having to go into an attic and down walls, it was much easier and made sense to run as many as reasonable.  Since I did the work myself and it was to local building code, I'm good.

Also, my house is the very first house load on the pole top transformer, I'm good.

Dedicated breaker boxes are a good idea if you don't have enough room in the main breaker box for additional circuit breakers.  Running a separate breaker box if you don't have room for the other can't hurt and should not violate building code as long as it doesn't exceed the mains capacity limit.

However, it is always safe to check with the local building code. 

Can't tell you how many times I've read about house fires where the owner had or did work that was in violation of building codes and if the insurance company finds out about the violation, you may not be covered.

anyway, dedicated lines do help.  At least they did for me.  Also, I compared four or five really nice power conditioners before purchasing the one I have and I really did hear differences.  Believe it or not.  

enjoy and be safe

Thanks minorl! I appreciate it!

If you have the space in your main panel for a dedicated circuit or circuits and don't have a very long or excessively complicated run, what is the logic for a sub panel?

As MC pointed out, it's just extra stuff.

With respect to following code, some of the setups I have read about on AG are irresponsible and downright scary! 20A outlets on 30A circuits! There are standards and ratings for a reason!

I have four panels, my very own high voltage transformer and a whole house generator. None of this was aimed at my system. Assuming your house was wired correctly to code, putting in a separate panel for your HiFi system will do absolutely nothing but waste money and any good electrician will look at you sideways and say something like, "are you out of your mind?" I can turn a 10 horsepower three phases shaper on and off and it has zero effect on my stereo. 
Good equipment does not need any of this power management stuff, none of it. Spend your money on good equipment not fixes for bad equipment. But to tell the truth I have never heard bad equipment need it either. 

If you have the space in your main panel for a dedicated circuit or circuits and don't have a very long or excessively complicated run, what is the logic for a sub panel?

As MC pointed out, it's just extra stuff

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True. If you have space on the main panel, wire the dedicated line on one leg and move the high-current devices and appliances to the other leg. It's been recommended to install these appliances as far as possible from the audio line on the panel.
I know, I know, these circuits are shared in the panel and not isolated, but there may be a benefit of less noise from appliances like a/c or furnace switching on and off.