I've had my Levinson 20.6's for almost 25 years and would never even consider selling. Have heard a lot of other amplifiers but none of them would make me retire the 20.6's. So I would be the last to tell you to steer away from Class A amps.
However, older amplifiers can cost a lot of money to service. Caps, diodes, trim pots and transistors can go bad after 20 plus years and it's not uncommon to get estimates in the $1000 to $2500 range to diagnose and repair vintage Krell, Levinson, Threshold, etc.
Is Class A the best design? Look at it this way: no preamplifier designer would ever build anything other than Class A. The only reason that power amplifiers aren't all Class A is because the dollar to watt ratio is too high and the maximum power is usually limited to around 100 wpc.
However, older amplifiers can cost a lot of money to service. Caps, diodes, trim pots and transistors can go bad after 20 plus years and it's not uncommon to get estimates in the $1000 to $2500 range to diagnose and repair vintage Krell, Levinson, Threshold, etc.
Is Class A the best design? Look at it this way: no preamplifier designer would ever build anything other than Class A. The only reason that power amplifiers aren't all Class A is because the dollar to watt ratio is too high and the maximum power is usually limited to around 100 wpc.