Is quality scanning with ND-3550A possible and reliable?
Possible yes, reliable no.
I agree with [B]vroom[/B] for DVD scanning.
For CD scanning the NEC ND-3550A is OK when scanning at 32x in my experience. It will show C1=BLER=E11+E21+E32 and C2=E32 which is the most one can expect these days. There can be occasional “phantom” spikes at some scanning speeds, and in my experience 32x is the scanning speed with least risk of getting such misleading spikes.