I also like the series 20 (23, 27, ref 20) amps. I currently own 2 pairs of Ref 20.0 and prefer them to the more forward sound of the 20.5 and 20.6. I do not think these amps are that great in terms of low frequency control though. Krell is much better in this department (same approximate years of manufacturing). They have a higher damping factor and just do bass better.
The 300 series was good but a little more analytical. Still had the "dark" characteristic of Levinson, but not as dark as the 20 series. It has better bass control than the 20 series.
As to the 400 series I have no experience with those. I also have no experience with the very early Levinson products, such as the ML-2.
The 300 series was good but a little more analytical. Still had the "dark" characteristic of Levinson, but not as dark as the 20 series. It has better bass control than the 20 series.
As to the 400 series I have no experience with those. I also have no experience with the very early Levinson products, such as the ML-2.