Well what you *need* depends on what you want. I. e. each DINx4 gives you 32 input pins (32 buttons or 16 encoders or any mixture of that). So first you should figure out what you want to build (how many pots, encoders, buttons, ...) then count the pins and then order the parts ;-) All the info on how many of [input thingie] can be handled by [input thingie module] can be found on ucapps.