For all its worth who cares about internal speakers , they're all incapable of showing what your keyboard can really do. There's so many choices for outboard systems from super compact to full out I would keep the keyboard if you like it and look in that direction. My Casio PX350 sounds OK with its internal speakers but nothing like the sound from my Carvin practice PA. Just my opinion.
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Bill in SC --- Roland BK9 (2) Roland BK7M, Roland PK5 Pedals, Roland FP90, Roland CM30 (2), JBL Eon Ones (2) JBL 610 Monitor, Behringer Sub, EV mics, Apple iPad (2) Behringer DJ mixer