McIntosh 501 or 602 for Magnepan 20.1

Don't even think about the Paraounds JC-1s on the 20.1s. I tried them and they were pushed to their limit. Their transformers are too small. They can't deliver enough voltage. You need a very powerful amp either a Classe Omega, Rowland, Levinson, or one of the high-powered ARC amps if you want tubes.

It won't be too much. It should sound a lot better with more power.
Yes, the JC-1 can run the 20.1s, but it doesn't control them the way a truly high-powered amp does. Just look at how little the JC-1s weigh. The real bruisers weigh 100-200 pounds a piece because they have big power supplies. I'm using the JC-1s on a pair of Magnepan 1.6s, where they sound much better.
Instead of getting another set of JC-1s, I'd save some money in your place and get the Classe Omicron or Omega, MK. 1. Far superior. I had them side by side. No contest.

I meant Classe Omicron or Omega MK 1--they're available for 5-6,000,
On my 20.1s, I went from Omicron MK to the mono pairs you mention. Yes, the monos are better, but the originals are not that far off.

I rebuilt the crossover and combined the internal and external and eliminated numerous connections. My reservation about active is that the only one that might be good enough is the Pass, costs $6,000, and I still wonder if it isn't as good as my retooled crossover. Though I will try active at some point.