sorry for the lack of any concrete information but I remember reading (years ago) in Stereophile or TAS that a costly crossover for the 20 (or 20.1) resulted in a minor upgrade. The concensus was that money was better spent elsewhere. I know the 3.6 and 1.6 can be easily upgraded this way but, according to this article, the 20.1 was apparently not.
Recommended crossovers for Maggie 20.1s
A number of contributors to these forums have voiced dissatisfaction with the stock Maggie crossover units. So what do you recommend as a replacement that would provide noticeable improvement? The Mye Stands have helped a lot, I could get larger amps (using Krell fpb 350 monos) but don't know a thing about crossovers.