I apologize in advance if this is clearly explained by someone in another post, but I've read through this board pretty thoroughly in an effort to not waste anyone's time.

I have a 2006 Mini Cooper S with both the OEM stereo head unit and the OEM navigation. it's a great car and I use the nav all the time, but I love music and the stock stereo just doesn't cut it for the amount of time I spend in the car. I've purchased an Alpine amp and two pairs of Boston Acoustics speakers to have installed by a professional installer. They're planning on inserting a line output converter and the Alpine amp between the head unit and the speakers.

Can anyone tell me their story of an install like this that went well, or equally important - if your install didn't go well, what should the installer avoid? I really want an upgraded sound system, but not at the expense of the full functionality of the OEM navigation.

Thanks in advance!
Tony