When I was looking for an amp to drive my Maggies 3.6, the A21 was one of my possible choices. When I weighted all the features and performance description for the amps I was considering, the Spectron seem like the real winner to me.
For my system, I'm pretty sure this is the right choice. It's been almost a year since I introduced the first Spectron amp to my system and I'm happy to report that these amps get better as the ancillary equipment gets better. I've been updating my ICs and SP cables to Stereovox Reference series and what I'm getting is a much more tactile listening experience. There is more realness to the sound with these cables. My point is that it seems to me that these amps perform extremely well with the best components out there. So I feel that if I bring a topnotch source or preamp, I won't feel the need to re-evaluate my amps. They simply get better.
I've listened to Kaya speakers driven by Innersound amps and they sounded pretty nice. They are great speakers and I'm confident they'll sound great with either amp. To these ears, the Spectron amps sound much more sophisticated than what the price suggests and therefore they get my vote.