The Dylan Amsterdam is definitely one of the best: http://www.dylanamsterdam.com. Very well located, but posh indeed... It's where Madonna stays for example.
The college hotel http://www.collegehotelamsterdam.com/ is another very nice one, and less posh. Located next to all famous museums.
Enjoy your time in Amsterdam! If you have any other specific questions, feel free to contact me.
Bart about 10 years ago