Why don't higher end amplifiers come with a separate power chassis?

There are some amp manufacturers who do think aftermarket power cords make a difference in sound quality.

Yes, The  AGD Audions come with quality power cords.

There are some amp manufacturers who do think aftermarket power cords make a difference in sound quality.

I do not doubt that for a moment. One thing is certain, confirmational bias is powerful. If someone is convince something will not make a difference, it certainly will not. This mindset can be extraordinarily rigid and unreceptive. Debate will be pointless.

Charles

@pwayland - The effectiveness of a tiny bit of resistance in the power supply to reduce or eliminate noise should not be underestimated.  DC sources with a tiny resistor in the way are going to perform much better in terms of noise rejection.

This is why it drives me a little nuts to see audiophiles trying to use car battery cables all the way to the transformers. The resistance and inductance between you and the rest of the world is a plus.

Frankly I don't see how marginally dripping the voltage with a tiny resistor is going to achieve anything.