Hmmm...I don't think there is an Amsterdam to Basel on Viking. There is an Antwerp to Basel, and that itinerary includes a visit to Amsterdam.
In Brugge, be sure to try the mussels and the fries (fries are served with mayonnaise rather than ketchup)...and have a Belgian waffle for dessert!
In Amsterdam, try to get to see the Ann Frank house and the van Gogh museum. And don't miss the red-light district at night. Like nothing you've ever seen in any other city!
The cathedral in Cologne is magnificent; the city is quaint, charming.
The music museum in Rudesheim is not to be missed.
Sorry, but I haven't been to Gouda, Nijmegen, Heidelberg, Strasbourg, or Basel...but they are on my agenda...