Welcome to the forums Cliff. I am an older gigging keyboard player playing in a 7 pc band. I have owned a good cross section of keyboard speakers and amps which has allowed me to play my keyboards through many combinations. In my opinion, most of the amps marketed for keyboards are nothing special, and they do not compare to a good self powered speaker. I assume you are not using a mixer between the BK9 and theB112, which is not optimum for that class of speaker. I assume you are also running in mono with the B112 for playing out, but at home you use a high quality 3 way stereo set-up but you gig in mono (?). Also assume that you depend on the B112 as your sole sound of gig amplification (?).
For live keyboard music performance , self powered PA speakers generally sound much better than packaged keyboard amp units. I've had PV, Roland, Fender etc combo amps and they served me well, but they aren't up to date technology. I don't recommend a packaged amp for keys if you want the best quality sound. However if you have to buy a packaged amp, check into Motion Sound keyboard amps (which are self contained stereo units). The stereo will sound much better to your ears, especially with organs sounds. These amps are not cheap but will do a good job. (Not as good as a self powered PA though). Is Motion Sound gear available in your country (?).
Your cheapest way to experiment is to buy a second B112 and a small stereo mixer (with tone controls and channel EQ). Set-up the mixer and speakers as you would a stereo system. Pick any 2 adjacent input channels on the mixer to use. Run LEFT OUT of BK9 to the ist channel, then run RIGHT OUT of the BK9 to the second channel. From the mixer, run one cable from MAIN OUT RIGHT to one B112 and run MAIN OUT LEFT to the second B112 speaker. Be sure all volumn controls are turned down before powering up. Put the mixer "PAN" control for both BK9 channels in "CENTER" position (equal L and R output). This sets a basic starting point to experiment with powered speakers connected to your BK9. * If there are any "mono" samples used in your keyboard, that sound will still be in both sides of this monitoring system. You can use the mixer to adjust the sound to your taste.
Just be reminded, the more gear you add the more work add to your set-up.
Mono versus stereo monitoring is an individual choice. I do it because my keys sound great in my stage space, and that is what I want to hear. My pianos, strings, horn etc really sound great and it inspires my playing. YMMV Don aka B3maniac