Most dedicated keyboard amps (with speakers) are generally nearfield and mainly considered monitors.
I think it also depends on the situation...in my case, using two powered stage monitors was ideal, as I only wanted the sound to project a certain distance. Those who wanted to hear music would be seated closer, whereas, those who came to the venue/restaurant to just talk, could be seated far enough away so that the music did not interfere.
"Studio" monitors and "stage" monitors are usually set up with different "throws", the latter tending to be longer. Studio monitors wouldn't work for my restaurant work...I tried a set of B&W D-110's powered by a 200 watt/side amp and they were unsatisfactory, at least for my needs.
Having used them before (rented), for stage use, I would seriously consider using two Bose L1 systems (in stereo), despite the initial higher cost, as they virtually eliminate the need for stage monitors, so money is saved in that area as is set-up/breakdown time.
Speaker systems are made today in many more (and often confusing) varieties, and custom installations are becoming the norm for many venues (house systems)....we sure have come a long way from the old Electro-Voice "Voice Of The Theater" speakers (and big old Crown amplifiers) we used to drag around back in the day.
Ian
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.