How good is your hearing ? And how do you know ?

Don't worry too much, as mentioned, I can currently only hear up to about 12k, and even to hear that I will have to really concentrate. But I could clearly differentiate between my Gryphon Mephisto power amp and my CH Precision M1 amp. Both being good power amps, but with different sound. So most likely it doesn't have too much to do with frequency, it's just a different sound, and some people will choose amp A, others amp B. 

Finally. Someone has a great transistor amp - Gryphon. How is FM Acoustics compared to Gryphon if you are familiar ?

@inna 
Unfortunately I have no experience with the FM Acoustics. Gryphon is great indeed, nevertheless, I'm now using the CH Precision M1. As stated before, both are very good amps, but my personal preference made me change from Gryphon to CHP. Still using Gryphon amps for the bass towers. 

han_n,
I see. Probably your choice of speakers also influences which one of the two you prefer. Swiss know transistors well, no doubt.

@inna 
Yeah, I'm using Gryphon speakers, it's all about having the preferable equipment combination for your own ears. It's not (or certainly less) important what others think.