audio upgrade, '96 318is

i'm upgrading the speakers in my '96 318is sedan, i'll also be adding an amp. i've decided to get 6x9's for the rear so will have to mount them high with spacers as they won't fit in the shelf, but for the front pods
which are under the dash by my feet i'm not sure how big i can go... they are currently 4" but the pods seem bigger... could i fit 5.25" speakers in there...?
also i have the factory head unit (blaupunkt paris RCM-104) with 10disc stacker, does this have RCA outputs to connect to an amp?

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