I'd go with the A21, certainly not the A23. A McIntosh amp capable of driving those speakers will cost at least twice as much. Also, first time I hear bright and lean in the same sentence with a McIntosh amp unless the amp was way underpowered for the pairing speakers. If anything, they tend to be more on the warm side of the scale, at least the ones I've heard/owned.
Odd question... power compared to?
I am saving monies for a high power 2 channel amp and am close to a Parasound A21... I have a Mac pre but can't afford a big boy Mac amp. A21 400ish per... would a lower power Mac do the same job as the big boy A21? I understand current ect. but I am hoping a more reasonable Mac would be in the same park... I had a 7100 Mac and my speakers ate it for lunch . What say ye?