I have always felt that bass rigs would be the best thing for keys as well..
Better than keyboard amps are for bass. But then again, bass amps have voicing and character, most are not "flat" at noon. Keyboard amps tend to have inputs more like a mixer.
When I first started, I chose a peavey kb300 for my guitar synth, figuring it would be good for bass. It worked for bass, but it had no punch or bite at all until I ran a guitar or bass preamp through it, then it was acceptable. I then put a peavey mynx 110 35w on top and used the preamp out into the kb300, that was a cool little rig until I sold the mynx. I used the kb300 on a few auditions, and finally joined a band with it, but before we got to gigging I bought my swr bass350 and a used peavey 1810 beast. No comparison. A few months later I had the stack of swr cabs.
But even with that punch and bite, bass amps are good keyboard and electric drum amps, just make sure you turn the tweeter on for that application.
Bass amps are good amps for anything.
Oh, the kb300 had an xlr mic input and reverb, I used it as a small pa several times, as well as when the drummer got some triggers. Other than the size and weight, I regret selling it, it definitely had some uses, 3 channels and 4 inputs (ch1 had mic and line inputs each with own gain)