It really depends on the designer/builder and your budget. For example the better stereo amps are "split down the middle" designs- isolated R &L channel amps on one chassis and often with separate transformers. Cheaper stereo amps share power supplies, caps, etc.
I have a buddy with no budget at all and he has 4 monoblocks. I can't really hear the difference at all. He can't either. He just likes the cool factor.
ARC's Reference line of stereo amps is so good you'd be hard pressed to hear the difference between them and their monoblocks.
Put another way there is a law of diminishing returns. 80% more money for 20% more improvement - but over what baseline? If your quality baseline is already a 9 out of 10 $50,000+ more for monoblocks is just tinkering and geeking out- not really a transformative action.
FWIW I wouldn't use a non-Mac upgrade if you're into the Mac sound. You could change the personality of the system and not for the better. Demo at home before you buy ALWAYS.