Hi folks, new to these boards though I'm a long-time reader, and will start getting into the discussion now that I've finally registered. In any event, I'm heading across the pond to meet a friend in Stockholm a few weeks from now. We have three extra nights (Sunday, Monday, Tuesday) after Stockholm to do whatever we want, and are trying to figure out where to go. Note that we need to be back in London by Wednesday night, where my friend is working abroad this summer.

A little about us: two 28-year-old males interested in seeing cool urban sites during the day, as well as partying at night. Both are important to us.

We've narrowed down our choices to three places:

1. Amsterdam
Pros: Obviously one of the party capitals in Europe with lots to do during the day -- Amsterdam speaks for itself. It also makes a lot of sense geographically, as it will make the return trip to London quick and easy.
Cons: Overrun by tourists in the summer season? I've also already been to Amsterdam, though it was a quick trip and I missed a lot of what I wanted to see (Van Gogh Museum, for one).

2. Budapest
Pros: A city I've been dying to see, with unique culture and nightlife. Will be lots to do both during the day and at night.
Cons: Out of the way geographically considering our Stockholm-London itinerary; two full days may not be enough to see such a large city, and I would want a trip to a place like Budapest to be all-encompassing.

3. Helsinki/Tallinn
Pros: Can take a cruise liner from Stockholm to Helsinki for a unique experience, then to Tallin, knocking off two countries that I otherwise can't imagine myself seeing. The close distances between cities makes this possible, though we would have really only 24 hours each in Helsinki and Tallinn. The cruise itself from Stockholm to Helsinki is a large part of the appeal.
Cons: Not sure how much there is to do during the day in Helsinki particularly that would interest us. Also, though I've heard good things about Tallinn's nightlife, I wonder what the party would be like on a Tuesday night. And this itinerary obviously would be tight.

If anyone has been to these cities and can speak to them, I would appreciate the input!

EDIT: I should note, I've done lots of research and am well aware of the top day/night attractions of each city, as well as the logistics of getting from place to place. What interests me more is the personal opinions of people on this board regarding which itinerary might be best.