They are different from what I understand. The one behind the seat is just a charger. I suggest that you look at a few after market additions to control or add music devices...
Clarion Remotes (need a Y cable, 30$) I bought the waterproof wireless remote.
http://www.clarion.com/us/en/product...tes/index.html
Accessories
http://www.clarion.com/us/en/product...ies/index.html
Bluetooth audio
http://www.sonicelectronix.com/item_...on-BLT370.html
http://www.kanexlive.com/airblue ( there are others like this )
GPS Bluetooth (requires Navionics iPhone app or other compatible map app)
http://bad-elf.com/products/be-gps-2200/ (there are others, I like this one)
eBay or Amazon have better prices than the sites above...make sure you buy the right accessory compatible with your head unit, likely the CMD6 Clarion.