I've heard the ML33 and the 33h, but not on MBL's unfortunately. The 33 was significantly better to my ears. Truly effortless.
I don't have experience with the A-50V but if it boils down to the 33 and the 33h - go with the 33's.
The numbers below are from memory but I know both of these amps pretty well.
ML33/ML33h
1. Transparency - 9/7
2. Detail - 9/8 (both very good)
3. Musicality - 10/8
4. Mid bass power - 9/7
5. Overall presentation up to 50-w per channel (remember, I don't listen loud) - 10/8
6. Stage depth - 10/8
Good luck with your decision.
I don't have experience with the A-50V but if it boils down to the 33 and the 33h - go with the 33's.
The numbers below are from memory but I know both of these amps pretty well.
ML33/ML33h
1. Transparency - 9/7
2. Detail - 9/8 (both very good)
3. Musicality - 10/8
4. Mid bass power - 9/7
5. Overall presentation up to 50-w per channel (remember, I don't listen loud) - 10/8
6. Stage depth - 10/8
Good luck with your decision.