Head Unit Upgrade - big P.I.T.A.?

[illanoize]

Hey all,
I've searched all over this site, other sites, and google, still can't find a straight answer for what I've been asking. I want to upgrade my '08 135i with an after market head unit. My does not have bluetooth, navi, or iPod controls built into the head unit. I would like this very much so. So, what is the down side of getting an after market head unit? What factory functionalities will I lose if I replace the factory head unit? If I replace the factory head unit, will I also need to replace the factory amp in my car? If so, will I lose any speakers (such as the one under my seat) in the process. Some of these may be simple questions that have been answered before. I just haven't found a post to cover these. Any answers, links to posts to answer my questions, or suggestions are welcome.

Thanks,
Illz

[ianc]

Interesting question which I don't know the answer to. If no one answers here, this is something I could see your SA answering if you called him with to find out. Keep us posted,

ianc

[Lester]

Do a search on 'Alpine 9887 headunit' , someone on this forum replaced their head unit with something from Alpine.

[john08135i]

As far as I have read you still need the OEM headunit just relocate it and you must extend the wiring to do so.