Here is another vote for the Plinius SA-102. As far as your question on the difference from A/B to class A, in my system it's quite noticeable. Much more subtle detail and more spacial clues. The definition of each note is more realistic. I must advise that on my older less revealing system the differences of the original SA-100 were not as pronounced but still easily discernable. I would not advise anything less than Class A if your looking for the ultimate and your system is capable of delivering.
Plinius class A vs. class AB sound difference?
I am considering purchasing a Plinius amp. I have read that many audiophiles do not hear a difference in an SA100 when it is switched between class A and Class AB modes of operation. If this is indeed the case, then would a Plinius 8200p (power amp; not the integrated) which is supposedly the same class AB circuitry found in the SA100, sound identical to the SA100?