Mark Levinson 20.5

What is the sonic difference between 20.5 and 20.6?

For this baby, I was told it runs hot and easy to have problem. Any experience or sharing on this? I am seriously look for it.

Current I own ML26s+23.5

Anyone ex or current user here????
ask at a Levinson dealer.

but the 23.5 has much power than the 20

the .6 is the last evolution : one card is changed - it semms that it sound better.
Any more comment?
I have owned a pair of 20.5s since 1990, and I still love them. As any pure class A amp, they do run warm. However, I had been listening to them at my dealer's for about a year when I finally bought them. They seemed to bring much of what tube amps brought without giving up what solid state amps had. As for realibility, I have never had anything go wrong with them, knock on wood.
Thanks. Anyone have bad experiences?