why balanced power last before component?

Here are the NEC requirements. You're not running balanced power everywhere, just the audio system, right? At any rate you might want to read all the way through:

NEC 647, which defines the requirements for balanced power systems, places some important restrictions on both their installation and use.

1. Conductors must be sized so that the IR drop does not exceed 1% of the line voltage under a load equal to 50% of the branch circuit current rating, and so that the
combined IR drop of the feeders and the branch circuit wiring does not exceed 2%.
2. A dedicated Equipment Ground conductor must be run to all equipment and each receptacle.
3. All receptacles must be protected by a GFCI.
4. The neutral must be bonded per NEC 250, and must also be connected to the grounded conductor of the circuit that feeds the system.
5. Balanced power systems are restricted to industrial and commercial occupancies.
6. All outlets “shall have a unique configuration” and must be identified using specific language called out in NEC 647.7.
7. There must be a receptacle having a grounded circuit conductor (i.e., conventional unbalanced power) within 6 ft of each receptacle for the balanced power system.
8. All lighting fixtures connected to balanced power must be specifically rated for 60/120 VAC balanced power, must “have a disconnecting means that interrupts all
ungrounded conductors,” and must be permanently installed.
9. Isolated ground receptacles are permitted. Balanced power systems are expensive, and their noise reduction capability is limited to about 10 dB. Isolated ground systems are generally a far more effective and less costly solution.

This might be old hat for you, but that final point is where I was going...

The final point is interesting.. but misleading -if I understand it to mean the maximum noise attenuation that can be provided by a balanced power system 10db. Can we agree that due to the physics of balanced power there is the potential for a range of "quality" for noise reduction achievable by balanced transformers? I'm surprised the NEC would make a 'blanket' assessment that "noise reduction capability is limited to about 10db". They're not identifying if they're talking about differential or common mode noise; nor specifying any frequency range(s)--both of which are necessary to make a meaningful statement. Don't you agree?

No, although more detail would be helpful.

The comments do support my view that individual grounding is cheaper and more effective. It would be nice to see exactly how though, as my opinion is based strictly on the observation I made earlier about center taps and these guidelines don't provide any supporting data.

The only reason you don't agree is your present lack of specialized knowledge about "Balanced Power". The statement that individual grounding is more effective is utterly untrue (and I wouldn't want to misinform through my thread). The EQUITECH website has technical articles that would help you understand more than you can discover by simply reading/paraphrasing parts of the NEC. I believe you would find it enlightening. It's also worth reviewing their list of clients, including NASA, CAL TECH, Gemini Observatory, Oakridge Lab, NSF, FAA and the US NAVY, UCLA, Princeton, NPR, and many more. A rather nice list of customers, wouldn't you agree?

It is a nice list of customers, but I think there is more to it than that.

I've read stuff off of their website but I see troubling comments. Here is one:

Can the problem of AC noise common in Class-A tube amps be addressed? How about noisy guitar amps?

The answer is of course 'yes' (BTW this is in the article 'lifting the ground', http://www.equitech.com/articles/enigma.html).

Fixing the problems in the quote is easy through proper grounding, and its not rocket science. I have found that a lot depends simply on whether the designer knows what he is doing or not- and has nothing to do with the AC power (and apparently, nothing to do with whether the designer is an engineer for a pro audio company or high end audio). A lot of noisy guitar amps are simply that way because they don't ground the circuit and the chassis properly. Class A amplifiers, FWIW are no more prone to noise problems than any other amplifier as the quote suggests. When I see stuff like this it makes me suspicious.

Indeed, further down we have this comment:

The power resembles a balanced audio circuit or an XLR input from an unbalanced to balanced audio transformer.

This is not true. If you want to do balanced, the thing you **don't** do is use a center tap! The reason is as I mentioned earlier- you reduce the CMRR figure significantly simply due to the fact that the center tap is not in fact at true center.

So when I see stuff like this I begin to wonder- does this guy know what he's talking about? Apparently he knows power but not balanced line operation...

What I am seeing here seems to boil down to this: If the equipment has design bugs in its grounding scheme, the balanced power will help. If the equipment has no grounding bugs, there will be no improvement.

This has everything to do with the fact that if the audio equipment is grounded correctly, there will be no current in the ground connection. IOW if there is current in the ground connection, you have a problem!

FWIW I have followed some threads on some of the grounding products like the Entreq Tellus. I did a survey of owners, who I asked to do some measurements for me. What I found was that in 100% of the cases where the owner reported an improvement through the grounding system, the audio equipment associated had a grounding problem somewhere in the system. I may be jumping to conclusions here but I am thinking the same thing is going on with balanced power. Its there to fix bugs in the grounding design of the associated audio gear.

IMO if there are such bugs in the audio gear, it should be fixed (whether the designer knows how to do that is another matter altogether). This will solve more than just AC power issues- it will also solve ground loop issues.