Alpine markets its head units as being able to seemlessly switch from one add-on input to another, but they simply don't deliver on the promise. If you want to add, for example, a CD changer, an iPod adapter, a USB adapter and bluetooth, you have to pick just 1, because all Alpine decks only have one Ai-net input, and NONE of the Alpine add-on units have Ai-net pass-through connections. Okay, so maybe Alpine sells a add-on with multiple connections---enter the KCA-410c. Buuuuuuuttttttt, Alpine blows it there too. First off, this thing's price, which is simply too much for what amounts to nothing more than an A/B switch, but the real problem is that it only expands the Ai-net inputs by 1. Gee, great, Alpine makes all of these great add-ons, but you can only use 2 of them at a time, and that's only if you pop $ for this adapter. Am I supposed to fork out another $ to add a third add-on (and that's on top of the price of the add-on), while cluttering up my car with yet another one of these units? If I want 4, I have to spend a lot of $ for 3 of these? That's pretty ridiculous, and I just don't understand how Alpine doesn't realize that this is a huge problem. This really takes a product line with huge potential and makes it simply fail to cross the finish line.