Becker CR-210 (1998 Boxster) modifications or replacement
 

Trying to upgrade the sound of my factory stereo, I was wondering if anyone has recommendations on:

- Replacement speakers (front & door); I assume there are no rear speakers installed, at least I wasn't able to find any

- Head unit: which product (if any) would be compatible with the factory 6-CD changer?

- iPod connectivity: any suggestion than the German adapter discussed elsewhere in this forum?

Any tips would be greatly appreciated :) !