Depends on your gigs, what you play and for how many and where. Don't waste your time with cheap gear. The BK9 sounds amazing and shouldn't be short changed by a substandard sound system. Thats why I think they left out on board speakers which would never do the keyboard justice.
Here's a solution for most arranger gigs.
Yamaha Stagepass 400i or 600i. Simple to use, easy and light to move, high quality stereo and not overpriced. And yes I would reccommend some light speaker stands to go along with it. You need to get the sound over your audience's heads so as not to sound muddy.
Bill in SC --- Roland BK9 (2) Roland PK5 Pedals, Roland FP90, Crate XP800 PA, JBL 515XTs , EV mics, Apple iPad (2) Behringer DJ mixer