Update 9/6: Removed 1 day from Amsterdam, now only 3 days.
Probably take the 8:25am train from Paris, arriving 11:43 in Amsterdam. There are enough trains that I could switch that to one that stops in Brussels if I want to stay there for a few hours, getting in to Amsterdam in the early afternoon instead of lunch time.
At some point I'm probably going to need to rent a bike. It's cheaper than taxis or buses and the city is really geared towards bikes (no pun intended). Frommer's says that "It’s possible to see almost every important sight on a 4-hour walk, and most people should be able to cover the center city on foot, though not all at once." It sounds like Amsterdam will be the kind of place that I can wander (as long as it's not raining).
Their three-day itineraries:
- Day 1: Van Gogh Museum, canal cruise, the Rijksmuseum, upscale shopping at Pieter Cornelisz Hooftstraat, strolling in the Vondelpark, the Anne Frank house
- Day 2: Amsterdams Historisch Museum, the Bloemenmarkt (Flower Market), the monuments at Dam, the Koninklijk Paleis (Royal Palace), the Nieuwe Kerk (New Church) and the Oude Kerk (Old Church), the Red Light District and "coffeeshops", and ending up in Jordaan (or some other neighborhood to walk around).
- Day 3: start at the Albert Cuypmarkt in the morning, then the Museum Willet-Holthuysen, walk to the scenic Magere Brug (Skinny Bridge), then check out the Hortus Botanicus (Botanical Garden), the Waterlooplein Flea Market for browsing and people-watching, Museum Het Rembrandthuis (Rembrandt House Museum).
I think I could easily spend a relaxing 3 days here, even without cutting out a day to make a side trip to Haarlem, The Hague, Delft, or Rotterdam, which I'm pretty sure I can avoid doing, but I did add a day off here. That makes Amsterdam days 11-14 of the trip.
My next stop is Copenhagen, Denmark. I can take the 7:01pm overnight train from Amsterdam (with a sleeper car surcharge on top of my rail pass), arriving at Copenhagen at 9:59am. Day trains transfer in Duisburg, north of Dusseldorf, and the ride passes near or through Munster, Osnabruk, and Bremen before another transfer in Hamburg, and then on to Copenhagen. The night train makes no stops but goes through northwestern Germany in darkness so I'd miss anything there is to see. If there is anything, I could take a more local train, but that would take longer since it'd have more stops.
Unless someone has a compelling reason for me to travel all day (or more) and/or spend time in Duisburg or Hamburg, the overnight sounds like a no-brainer. I'll come back to Germany two other times later, going to Berlin and Munich.
Unfortunately this only gives me 10:43am on 9/27 to 7:01pm on 9/30 in Amsterdam, or just 2-1/2 days and 2 nights. Ah well, if I want to spend another full day here, so be it.