I have owned 2 Alpine decks before. When I checked into CD changers for them I found out that there are only a couple of changers (both made by Alpine) that would work with the decks. Otherwise you would need a whole seperate control unit for the changer. otherwise I would stick with Alpine for a changer. I've dealt with a Pioneer changer before and it felt cheap and flimsy like it could break at anytime so I wouldn't recommend Pioneer.
Stick with a changer of the same company and the same year. Alpine changed their net protocols a few years ago so make sure the changer you get is the correct protocol.