Great information here. I was (“was” being the operative word) considering purchasing a second a21 and running it in bridged-mono with a pair of Thiel cs3.6 loudspeakers....until reading the comments here. I was using an a52 and, they sounded pretty good and then I got the a21 (not the a21+). The difference was amazing!!! The Thiel’s are 4 ohm but, I’m sure at times they “see” considerably more resistance. So, I may buy the JC1’s sometime in the future and just enjoy what I have which is a pretty remarkable sounding 2 channel setup.