Is there actually a difference?

Back  when I was young many years ago I could here all sorts of differences between amps. In the pre-nineties days the big amps often didn’t sound near as good as the low wattage four output transistor 60 watt class!
In those times interstate coupling caps were common and caused degradation. Around 2K many companies had adopted direct coupled designs with dc servos on the outputs. All at once amps sounded much cleaner, even the big amps were much improved. (Yes I know I’m oversimplifying!)
In recent years I found out about level matching amplifiers (within .003 volts) from Van Alstine. (Wish I’d known sooner.) Using his methodology, most modern amplifiers I’ve compared sound very similar in the mid frequencies. I think due variances in output impedance and how an amp interacts with a speaker’s modulus of impedance there are audible differences mainly in the frequency extremes.
 I think those who hear dramatic differences in amp sound are using a speaker with a difficult load. I’m not surprised when Alan Shaw has no winners of the Harbeth Challenge. Those speakers are such an easy load. I suspect any reasonably good modern amplifier would sound almost identical! Good discussion.

This specific subject has been discussed and debated here, and everywhere. I know my systems, I know my music, and I trust my ears. Taking 1 piece out and replacing it with another piece, whether it is an amplifier, or an interconnect, I hear differences. Determining which I prefer, that is for another discussion, but differences, are easily audible. Enjoy ! MrD.

tomfoolery,
Very interesting info, I'm not familiar with level matching....will have to look into that. And this is a great discussion for me as it's primarily what I'm concentrating my efforts on now. Here's been my experiences...just my two pennies.

1. The very best system I've heard had a tube amp. Not going to argue the merits/faults of tubes but it just sounded incredibly musical and captivating to me. 
2. The next best systems I've heard had class A amps. They seemed to come close to the sound of tube amps.
3. A/B amps of various brands and quality seem like they can get closer to a class A amp. 
4. Class D I have no hands on experience with other than what I've read. 

So my "unicorn" system would have the efficiency of Class D, would sound like a tube amp, but would also be able to be switched to sound like A/AB for home theatre and some types of music. Impossible I know, just wanted to expand on the OP's question of differences and hear other's thoughts on the above "class warfare" lol. 

There is a difference. Most systems benefit from having an amplifier that has characteristics that optimize the sound of the speakers (in your room, playing the music you listen to, at volumes you are comfortable with).

Your listening habits, room and speakers will make much more difference, provided you are using a well specified amp that can produce the appropriate amount of power. The quality of your program material will also make a huge difference.