All amps built based on hi-fi specs will sound the same if theyare tested on controlled environments.
But you should note some amps, especially the expensive ones, are not necessarily built with common specs (strict hi-fi spec compliance - if ever there is a real one!) in mind. This is what we call their sonic signature. And sonic signature is sometimes the 'thing' that some audiophile run after - especially on tubes.
For the group who can afford much, the ownership of costly amps (which include BOSE
) is part of pride in owning aesthetic products or expensive gears. Cost, again, is not even a factor of sonic performance - probably of built quality (which I also doubt - like the BOSE and the gain card and the exotic cables). Perception varies among consumers!
If you are just into good performances of materials by your audio gear - better filter your information among the reviews that you read or the recommendation you hear. They are part of the game in commercialism (aka profit orientation of businesses) even in audio industry. Buying is an art, listening is an art - but buying and listening are 2 different things.