I wouldn't stay in Amsterdam for more than 1-2 nights to see the main museums and the canals. The rest is cheap rubbish. If you want to see Europe, this should be part of your itenary:
- London
- Paris/Versailles
- Barcelona
- Venice
- Florence/Siena
- Rome
- Vienna/Salzburg
- Prague
- Interlaken/Alps

Consider buying a car to do this 'Grand Tour', and sell it afterwards.

Cheers!

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2011 Prius