You need to check out this link!
http://forum.ecoustics.com/bbs/messages/4/137782.html
The "ERR2" problem appear to be
VERY wide spread!!!
While there are a number of posts (100+), the general message is that the CD changer that Nissan/Infiniti selected for use with the Bose system (made by Clarion) in their cars/trucks SUCKS big-time!!
Currently, only one of the posters has any kind of resolution.
In response to your original question (keeping the speakers), if you read through the messages, you will see a reference to an adapter that Crutchfield carries (
http://www.crutchfield.com/S-2u34RgE...sp?i=142C4NN03 ). It's a possibility.