Several comments:
1) You are in the price range of the Pass Labs pure ClassA vs ClassAB amps. They are different, and I would try them. So, for example, XA100.5 or XA160.5. The Maggies have such a pure upper midrange, and pure class A makes that sing quite beautifully! Note I would rather have ClassA at lower watts than ClassAB. However, I have Maggie 3.6s, not 20.1s, and with push pull and all that, maybe you need even more watts.
2) If you want to hold yourself over for a few years try Innersound - they are relatively cheap used and compete with the big guys when used with Electrostatics quite well. They may be half or a third the price of the big guys but are at 98% or 95% at the least of the quality.
3) I'm curious about ClassD. While I love my big PassLabs ClassA amp and all that comes with it, I've heard that ClassD stinks for MartinLogan/SoundLabs but there is sometihng about the load profile of Magnepans that are different and they can be used. The reason I mention this is that you can get ridiculous amounts of power through Class D, and with the 20.1s that might be interesting.
Also - there are professional ClassD amps that I would love to compare to 'audio' amps.
Professional Class D amp:
Crown XLS 5000 in 4-Ohm Bridged Mono mode: 5,000 watts
Crown Dsi or Cts - both have 'low ohm' modes, 2,500 - 5,000 watts depending on how you hook them up.
QSC PLX2 3602, 1800 W @ 2 Ohms, 1100 at 4
Audiophile Class D amps to consider:
BelCanto REF1000 MKII: 1000W, good to 2 Ohms
(and this is a gen 3 Class D amp, and it is analog-controlled, not digital controlled, I hear that is a lot better, and they've figured a lot out since gen 1)
Rotel RB-1091 - 1000W at 4 Ohms. Rotel with a 20.1? Hereasay? Could be, but still - this could hold you over for a few years, and you'd be playing with 1,000 watts! I'd go with the BelCanto, but as a holdover amp, this would be 'fun'.
Personally, I'd just get the largest Pass XA.5 that I could afford, or 4 of them with active bi-amping via Marchand or Bryston. If you have money leaking out of your wallet, get the Pass Labs crossover, it has no competition.
Maybe head towards bi-amping right away. Then something like the Rotel isn't so crazy, as monoblocks you need 4 and if these are 10k each, that is a lot of cash. Then you can dial in the crossover for a while, then upgrade the amps - and anyhow it sounds like peopel spend a lot of time getting bi-amping right and the Rotel's would hold you over during that period.
If you have the room in your house and the inclination, go for 20.1 vs 3.6. Push pull is definitely different. However, if you are money constrained (many 20.1 owners just aren't) one could argue that 3.6s with the difference in cost applied to amplification, would ultimately sound better.
1) You are in the price range of the Pass Labs pure ClassA vs ClassAB amps. They are different, and I would try them. So, for example, XA100.5 or XA160.5. The Maggies have such a pure upper midrange, and pure class A makes that sing quite beautifully! Note I would rather have ClassA at lower watts than ClassAB. However, I have Maggie 3.6s, not 20.1s, and with push pull and all that, maybe you need even more watts.
2) If you want to hold yourself over for a few years try Innersound - they are relatively cheap used and compete with the big guys when used with Electrostatics quite well. They may be half or a third the price of the big guys but are at 98% or 95% at the least of the quality.
3) I'm curious about ClassD. While I love my big PassLabs ClassA amp and all that comes with it, I've heard that ClassD stinks for MartinLogan/SoundLabs but there is sometihng about the load profile of Magnepans that are different and they can be used. The reason I mention this is that you can get ridiculous amounts of power through Class D, and with the 20.1s that might be interesting.
Also - there are professional ClassD amps that I would love to compare to 'audio' amps.
Professional Class D amp:
Crown XLS 5000 in 4-Ohm Bridged Mono mode: 5,000 watts
Crown Dsi or Cts - both have 'low ohm' modes, 2,500 - 5,000 watts depending on how you hook them up.
QSC PLX2 3602, 1800 W @ 2 Ohms, 1100 at 4
Audiophile Class D amps to consider:
BelCanto REF1000 MKII: 1000W, good to 2 Ohms
(and this is a gen 3 Class D amp, and it is analog-controlled, not digital controlled, I hear that is a lot better, and they've figured a lot out since gen 1)
Rotel RB-1091 - 1000W at 4 Ohms. Rotel with a 20.1? Hereasay? Could be, but still - this could hold you over for a few years, and you'd be playing with 1,000 watts! I'd go with the BelCanto, but as a holdover amp, this would be 'fun'.
Personally, I'd just get the largest Pass XA.5 that I could afford, or 4 of them with active bi-amping via Marchand or Bryston. If you have money leaking out of your wallet, get the Pass Labs crossover, it has no competition.
Maybe head towards bi-amping right away. Then something like the Rotel isn't so crazy, as monoblocks you need 4 and if these are 10k each, that is a lot of cash. Then you can dial in the crossover for a while, then upgrade the amps - and anyhow it sounds like peopel spend a lot of time getting bi-amping right and the Rotel's would hold you over during that period.
If you have the room in your house and the inclination, go for 20.1 vs 3.6. Push pull is definitely different. However, if you are money constrained (many 20.1 owners just aren't) one could argue that 3.6s with the difference in cost applied to amplification, would ultimately sound better.