Suppose you have an amplifier that takes a standard, unbalanced, analogue line level audio signal via RCA terminals.

What I'd like to understand is what determines the maximum strength of this signal that the amplifier can handle before the amplification is clipped. Also, is this max oriented on voltage? or amps? or wattage? or ...?

The question is not in connection with a particular project. It's just something I'd like to understand better to the end of better designied audio systems. Much appreciate any input.