CD changer advice please

Ive got the standard headunit in my car currently, and have never liked single disc cd players as the disc are quite big, and where do you put them? Which is why a couple of years back i got a MD player for my old saxo, as they are alot smaller and no problems with scratches.

Anyway fitting a cd changer seems to be the easy option but i'll still need to carry some cd's around they dont need to be visible in the car. But i've tried to follow alot of the comments made about cd changers but is there an idiots guide to fitting one? If it fits under the passenger seat surely the 'cubby hole' has to come out? What is the cd changer fixed to? the floor? the seat? where do you run the cable to the HU?

Arnt there specific model cd changers that work/fit?

Seen a few advetised on Ebay which have caught my attention and am getting tempted!