I use blue tomato dot com (hotlinks don't work here?) Especially the discounts they have are quite interesting. There's also two decent snowboard stores in Amsterdam but those are quite pricey and one of them only has certain brands.
Concerning boots, I would recommend Salomon boots any time. The girl boots are pretty, affordable and super comfortable.. its a freestyle orientated boot though (so its not super stiff) but it keeps shape like forever. Mine are starting to fall apart a little bit now but I practically live in them haha.