While I don't have any experience with the 680MP, I did own the Pioneer Premier DEH-P8MP for almost 2 years. I bought it brand new and it served me well, if you're looking for a deck to play MP3s, look no further, that thing read a full mp3 disc within like a second. Anyways, for tuning and features and stuff, the 6.5 volt pre-outs are nice and navigating through the menus takes a few days to get used to and then it becomes second nature. The 1 big knob thing was confusing at first but Pioneer is really liking that design this year so it must have sold pretty well right? I personally liked the design of it, it was sleek and simple, overall, I'd buy the same deck again if I had the chance. Message me if you have any more questions!