AMS actually has very comfortable loungers, and some leather couches, in public areas (couches are near the lockers, just a 2 min walk from McDonalds) making AMS one of the easiest airports to sleep in. The airport is well lit, safe, ou can sleep air-side. Security is out on patrol, and will even stop ,sit and chat with overnighting pax who are awake.

Skip the hotel, stay in the KLM lounge until they toss you out at 11:00pm. Go lock yourbags, sleep on a couch or lounge and go back to the lounge when it opens again at 5:00am for a shower.