Just spent 3 weeks. Do yourself a favor and don't waste too much time searching. Go to Grey Area, and get Grey Myst or 4077 Medicinal Leaf. Most consistent shop I visited, and both of those choices were the best I found the whole time. And I went to a SHITLOAD of them during the trip (I called my trip "three weeks and 100 grams"). Other favorites include Greenhouse Tolstraat (Northern Lights X, and the best relaxed vibe), Katsu (Killer Green), and De Dampkring (good general selection and really cool interior).

Barney's has the best hash. WARNING: Ice Hash is like "Hash Crack". I literally watched a buddies face turn ghost white on 1 puff of Barney Rubble. Take it slow if you aren't used to this type of stuff.