Atmasphere, I read your last post again - are you trying to say that even when nfb decreases the voltage drop due to increased current output (the Zout), that doesn't mean that the amp can all of a sudden deliver more power? If so, I fully agree. The amp has it's intrinsic limits in output current and output voltage and nfb cannot change that.
Even with nfb, when the output voltage goes up, it eventually gets up to the supply voltage and cannot go higher of course. Same with the output current - the current capability of the amp cannot increase due to nfb. What nfb will do is to keep 'trying' (if you will excuse this antropomorphism) to keep up the output voltage right up to the supply voltage. This is, of course, the reason why an nfb amp generally clips much sharper than a non-nfb amp.
Even with nfb, when the output voltage goes up, it eventually gets up to the supply voltage and cannot go higher of course. Same with the output current - the current capability of the amp cannot increase due to nfb. What nfb will do is to keep 'trying' (if you will excuse this antropomorphism) to keep up the output voltage right up to the supply voltage. This is, of course, the reason why an nfb amp generally clips much sharper than a non-nfb amp.