I'd advice "de tweede kamer". It's in a small sidestreet to the Spui, or their sistershop "de dampkring" which is near and it's a bit bigger. Those are two of the best in Amsterdam. Best thing is, they'll give you exactly what you ask for, describe them taste and effect and they'll show you the choices which comply to your descrïption.
A small warning. I've lived for a couple of years in Amsterdam and I remember sometimes tourists came by, asking for their strongest stuff (mostly Americans) and they also got exactly what they asked for.

So be exact in your request.
I guess you've been in Amsterdam more often, so you'll know the first rule for Germans in Holland: Speak English.