Wow, thanks a lot for all the replies!
So I'm going to have a look at the prices for the 17-40L. They vary quite a bit. Or maybe try to pick up a good second hand one. My tickets to NY were 200€ more expensive then I expected, so I'll try to find a good deal. I have quite a large shopping list (eg Pelican 1514, which is around 200$ cheaper in NY than in Belgium), so I'll have to watch my budget for the next months