I don't think the driver has to be the same, yes in a perfect world it would be nice to have matching sub's, but for most of us it may not be possible. I have a infinity csw10 up front with a polk psw404 in the back (yes they are the same size of driver but different brands and power ratings), it did take some time to match levels and placement but the bass is just killer with the two subs, the csw10 alone was probably fine but the two are incredible.