Lise, may I suggest, perhaps, that you buy him a gift certificate to put toward a classical guitar? If he's been playing for some time, then he will likely want to try the guitar out before he makes a purchase. I know gift cards aren't seen as being quite as thoughtful, generally speaking, but I think that when it comes to personal choices like musical instruments giving a gift card shows that you want to make sure it's exactly what he wants. And you could absolutely go pick it out with him, of course. =)
That's what I'd prefer, personally.
Peace,
James