I'm having the same problem. The PX-s7000 sounds awesome on my headphones but not full and warm through the speakers. It may have something to do with the fact it's standing against a stone wall and on a wooden floor. No curtains or rugs or anything. I asked Casio Support for advice and they said a subwoofer is not needed because the keyboard doesn't go into such a low frequency range. They advised to look at a three-way system like those from Logitech. Remarkable because in my opinion Logitech only makes cheap systems for computers. Has anyone suggestions for another (small and preferable harmonius mustard 🙂) speaker system that fits the PX-S7000. Or would a subwoofer indeed be the solution?