Agreed. Sometimes the differences are subtle, sometimes not. There is a kind of vaguely generic amplifier, but a) some aim at a particular market: b) circuitry arrangements are different - there's still a lot of debate about what's good and not; and c) the best amplifiers don't always use the best components (unless they're fashionable, like huge capacitors that precede a regulated power supply).Wow, no, fjf, that really goes against all my experience in listening to amplifiers, both of the same and different brands. The differences between many amplifiers are in no way subtle.f
Some people can't tell the difference between amplifiers of the same technology, others can. My associate (with who I design and build) can genuinely tell the difference between two of the exact same make/model of some vinyl cartridges let alone different makes (in most cases. Ironically it's the cheaper ones of the same make/model number that defeat this particular skill).
There may come a time when amplification circuitry is so modularised / built of identical (quality/value) components that sonic differences could be disregarded but that isn't the case at the moment. Class D power amps are under the spotlight at the mo. They haven't quite won me over yet....
If amplifiers were truly transparent there'd be no further need for design effort. I tend to agree with bigshot that there's an awful lot of trivia, chicanery and charlatanism about audiophilia but beyond that, some of us are still striving to achieve the transparent amp: the straight wire with gain and no resistance.
Ultimately it comes down to your personal taste and this can only be exercised by listening - and really in your own room. Again, as bigshot pointed out elsewhere, the sound of a system will depend on room-tone.