6 disk cd changer?

When i just recently bought my 2000 celica it had a 6 disk cd changer in the trunk and a normal looking deck it just doesn't have a place to put a cd. I want to change out the deck for a better brand name but i have had 2 or 3 car stereo places tell me i can't. All i want is a deck that will hook up to a 6 disk cd changer can anyone tell me what kind of deck to look for?