A21 vs McCormack?

I will also recommend McCormack and SMcAudio, as the work they have done for me is beyond reproach.
I have no knowledge of Parasound, but have known the brand to be of very good quality.
The question is what are the other components of your system?
I hate the trite term 'synergy', but it really does come into play.
Bob

@cheeg, 
For the money, I would get an Ayre Codex for a DAC.
Used, they are just a bit above $1K these days.
Or, a Schiit Gungnir or Yggy.
Both companies offer upgrades, and have very detailed sound, in my humble opinion.
Also, if you can ever score a broken DNA-1, SMcAudio can convert them to monoblocks. All they need is the case, everything gets scraped and overhauled. They did a pair for me a couple of years ago.
Just be sure to tell Pat or Steve what equipment you are using, they can tailor the amp to whatever you own.

As far as Class D goes, I would give it a couple more years to mature.
Yes, they can sound great, but I think staying with A or AB amps would be the safest course, for now. Again, just my opinion.

Bob