I looked up the weight of the keyboard .... 22.5Kg (49 lbs. 10 oz)
I have a pair of speakers that are intended for use in a vehicle, have a woofer and tweeter similar to what looks like the PSR9000 has and are housed in molded plastic case. The combined weight for the two with the case is approximately 2.7Kg (6lbs). I'm guessing the two plastic cases may be about 0.68Kg (1.5lbs) total together, so the set of speakers minus the case might be about 2.0Kg (4.5lbs) and that estimate may be on the high side. Is it worth tearing down the keyboard to remove the speakers and possibly only save 4 lbs?