if by "gain" you are referring to the "input sensitivity" of the amp to reach it's rated level (i.e. somthing like 1.5 volts, more or less) then the answer to your question is yes, except that the less powerful amp would clip earlier. Your latter observation is likely due to the current requirements of your speakers - all watts arn't equal (it might also just have a lower input sensitivity and thus seem to be more powerful.)
Amplifier "gain" question
Currently using a Classe 301 300 watts per channel amp for my front two channels. Thinking about picking up a Classe 201 {200 watts} for the rear channels. On the spec sheet they both list the same spec under "gain" . Does this mean under normal listening conditions their volume output would be similar. Prior to owning the Classe 301 I had the Rotel which was rated at 385 watts per channel, yet the Classe 301 despite being rated 80 watts less , puts out more volume with less stress.