Have you checked with a group called Atlantic Fellowship? I have used them for more than 20 years and know they are very reliable. They are based in DC at Kalorama. I find they can get cheaper air tickets that most. They are consolidators. Here is their website: http://www.atlanticfellowship.com

I just looked and it seems they have a special to Amsterdam. May not be your time but you can also call them and they are most helpful. Phone is 202.232.6990

Good luck! Nancy in Alexandria VA