What kind of effort level are we talking about for the installation...?
If I didn't go with the full package (change all the speakers), which are the key ones to change out to get better sound, or do they all really need changing?

How do you figure out which speakers will fit? Is there any dimension info for the factory speakers around, so I can make sure any new ones I buy will fit and are the correct impedance?

Also you mentioned that speakers would be louder if the new ones are lower impedance. I will probably not take a chance on that, will just match the ratings on the new and old speakers. Question is, what are those ratings?

Thanks to people who responded.

TTM