My original C1's always sounded better the more you turned them up. That was fixed with the MKII/Signature. But I think the problem is with your amp. I had a Bryston B100sst and although it sounded very good with the C1's it wasn't the best for me. It lacked the 'control' over the music. I ended up with an Octave V70se w/black box. Less watts (180 vs 70) and the Octave in my opinion just trounces the Bryston. But that was also going from SS to Tubes.
That being said most Dyn speakers are somewhat laid back (so to speak) when compared to B&W or Focal (just a couple of examples). I say laid back because they are not forward in any of the frequency ranges. Some may refer to that sound as uninvolving. To me the Dyn S25's Sapphires and Consequence UE are more lively with a punchier bass - more forward upper mids and the highs that have more 'sizzle'. I prefer 'sparkly' highs. I like them all but in the long term I never get fatigued even after 14 hrs. The Sapphires on the other hand sound great but for me only in the short term. So all and all after upgrading to the Octave and C1 signatures I listen to the music again and not the individual instruments - vocals and equipment.
That's my opinion
That being said most Dyn speakers are somewhat laid back (so to speak) when compared to B&W or Focal (just a couple of examples). I say laid back because they are not forward in any of the frequency ranges. Some may refer to that sound as uninvolving. To me the Dyn S25's Sapphires and Consequence UE are more lively with a punchier bass - more forward upper mids and the highs that have more 'sizzle'. I prefer 'sparkly' highs. I like them all but in the long term I never get fatigued even after 14 hrs. The Sapphires on the other hand sound great but for me only in the short term. So all and all after upgrading to the Octave and C1 signatures I listen to the music again and not the individual instruments - vocals and equipment.
That's my opinion