Is the radio replaceable in the 850 with a double DIN or is it some insane fit where you have to get a factory radio? Are there built in amps for the stereo that i would have to disable?

The radio in the 850 is a standard double DIN size. You can fit a double DIN radio but i reccomend getting a single DIN and going to almost any car audio shop and ordering a single DIN conversion kit which just covers the extra slot quite nicely. When changing radios you will loose your factory amp but you dont have to disable it, there just isnt a place to plug it in to in an aftermarket radio. You will loose a bit of bass but overall if you get a good radio the sound quality is much better.

Mark 96'854T-5
83'760Ti

Thats great to know. I want to get one that will look good with the style of the 850. My goal is to be able to play MP3's on it, but those usually arent very high quality so i dont know what i'm going to do. I should be buying my 850 in the next week or so. Finally sold my nissans and taking the volvo plunge.