For which of your BMW's you need speakers? The whale ('85) can be set up with bigger speakers than the shark ('80)
http://www.rondevries.nl/index.php?page ... bgroep=129
Within this link you will find 4"x 6" speakers. You should take one with the 90 or 91 db sensitivity. Also take into account the mounting depth, for the whale the Polk compo will be good. the JBL might fit the shark, but i am not completely sure about the mounting depth