For what it's worth, I recently acquired a Concentra I, and, in the context of my system, found it to be far superior to the Sim I-5 and an earlier Bryston (b60). I am of the opinion that system synergy is THE most important variable, so, if at all possible, audition the component in your home with your associated gear. Finally, I'd say that the Concentra, like many SS amps, is likely to match up best with sources which lean to the warm side.
Tony
Tony