To answer your second question first. Yes. I have installed a cryo-dipped hubbell IEC at the end of my 20amp dedicated line and plugged it directly into my amp.
It wasn't pretty. It took all of about 5 seconds to recognize the negative sibilance without my passive in-line conditioner in place. Not to mention the other negatives such as raised noise-floor flattened and shrunken soundstage, etc.. Even a good aftermarket power cable will probably offer sonic improvements over the straight service panel to amplifier strategy.
As for your proposed alterations, I would do everything reasonable to keep the components close and the cabling short.
Not to mention that it sounds like you will not have any properly constructed racking system for your components. Therefore, all air-borne vibrations will remain trapped within the components and reek havoc at the micro- and even macro-dynamic levels. (it appears that some people prefer this)
As for your last question, I would guess that one would want the service panel as close to the components as possible. So as long as the service panel was at least 3 or 4 feet away.