What if all amps sound the same? That, is, no sound of their own as long as the amp is one of hundreds of quality amps with no audible distortion, and the amp is being operated within its capabilities?
Consider: "Any amplifier, regardless of topology, can be treated as a “black box” for the purpose of listening comparisons. If amplifiers A and B both have flat frequency response, low noise floor, reasonably low distortion, high input impedance, low output impedance, and are not clipped, they will be indistinguishable in sound at matched levels no matter what’s inside them."
http://theaudiocritic.com/blog/index.php?op=ViewArticle&articleId=38&blogId=1Of course, operating at "matched levels" is critical for proper evaluation. One unit that is even subtlety louder will seem to sound better.
The characteristics some feel makes certain amps (or other equipment) sound better to them might be the low level of distortion that equipment puts out...sounds better to some folks over certain loudspeakers, and that distortion (coloring of the sound) does not sound good to other folks or over other loudspeakers.
So, I'd buy the lowest cost quality amp I could find that has adequate power, and avoid any amp that has any characteristic sound of its own.