Brecon

Hi I have been trying to wade through the internet to make sense of all the different comand units available for the S-Class. My car is already fitted with the comand 2.5 (A 220 820 46 89) which was factory fitted. I wanted to upgrade to the widescreen version 16:9 and find there are two models, almost identical except the knob on the bottom right is more of a joy stick and has the APS added on, I think this means it is DVD compatible but not sure. My question is I can buy a Used comand model number is:- A 220 872 20 42. Can someone please shed some light on what I can use and if this model is any good for my car? Any help would be appreciated.