chances are the Piezo will be a little hotter than the Pioneer. would need efficiency specs for both speakers to know for sure which one will need attenuation. there are a ton of post on the Pi forum on piezo's that you could search into. if you want to play around. just hook up both speakers together. the piezo does not need a capacitor to protect it. I have added a piezo to a system before for a little extra top end performance. I have used a 1uF cap in series. this will attenuate it and give a higher xo point. the piezo doesnt act like a normal cone speaker. read up a little and play around. you cant hurt it.