e46 speaker size

[DHW BMW328I]

Hey guys I have a 99 328i & i'm upgrading the sound system. Does anyone know how big I can goes with the factory speakers ? I looked it up & it says the factory speakers are Front 5 1/4 3 1/2 Rear 4" Is that the largest I can go ? I have the rest of the system All Alipne I'll post the pic after all is installed ....
I've done alot over winter : DVD, Monitors in headrest, Rearview Mirror Monitor, Alpine Navigation System, M3 Lip Spoiler, Now it's time for the sounds. I appreciate any help you guys have on the speaker size .....

[HFR]

at least in europe, the size is 6inch both in the front doors and rear deck.