I've been wanting a couple of guinea pigs for ages, and dh has just agreed that I can have some for my birthday in a few weeks. 

So now I want to make sure they will be happy, and I don't really trust the pet shops to give the best advice. What cage would you get for 2 little guinea pigs? They'll be indoors all year round, we've got a reasonably big space in the dining room for them to live in, and will let them out to roam the kitchen/dining room every evening.
I'd love any other advice you can give me as these will be my first guinea pigs.