480 (AB) or 650 (A) is really a question of taste.
You can do the same with a P-4500 versus a A-47 (or A-48).
And go up higher the ladder.
I tested all this, and I prefer the AB-class, but probably being an exception...
Everybody runs for the class A when it comes to Accuphase.
The AB have not the same reputation and are more difficult to re-sell!
BUT: like with cedar or spruce in guitars, the best is to have both
