Speaker up grade for doors and rear ?

Hi all
  I'm after some 2way speakers to straight swap into place where the factory ones are.   I just have a ordinary Blaupunct tape deck and no amp .    I bought a pair years ago for ?50 but do'nt remember where.
         Thanks for any help
                            Ali

I bought Infinity Reference 6"x4" speakers and they are definitely better than the stock fitment. Bear in mind, unless you are prepared to enlarge the surrounding hole behind the metalwork (hacking into the bodywork) you won't be able to achieve decent sounds, because you can't fit in bigger (=decent) speakers.

Maybe something worth exploring is to try obtain and fit speaker pods and pockets from a Rivage, they had 13cm squawkers and tweeters in them.