Many keyboard amps will not have the sonic clarity that studio monitors do. They're fine for practice - but you will find properly matched studio monitors to provide the most detail and intended sound (the instrument was likely developed/"tuned" using Yamaha studio monitors). The nice thing about keyboard amps is you can grab a handle and "everything" comes with it. Often they have mixers integrated so you can connect multiple keyboards and/or vocals as well. Most keyboard amps are stereo - although speakers are close to each other (so physical separation is limited to how the amp is built). Some have effects which are OK for vocals - your keyboard likely will not benefit unless the effects can somehow compensate for the "lower-fi-ness" of the keyboard amp vs. studio monitors (don't count on it). I'm alluding to here the "wide" stereo mode that I see with one keyboard amp example. Maybe that would be something that would benefit, for example.

I'm not sure "most" keyboard amps are stereo, but I agree, even when they are, the stereoness is usually questionable. An unusual exception is the Spacestation, which gives you a nice spacious stereo effect out of a single box. But for sheer sound quality, nothing beats studio monitors for home use, or quality full range PA speakers for gigging. Keyboard amps are notoriously less neutral sounding.

OK, Jason and Scott, thanks.

... if you want true stereo out of some of the Roland amps - you use something called "stereo link" - which is basically a daisy-chain of one of the channels from one amp to another amp. So you would buy two of the one-speaker boxes and carry around those to your practice.

There are ones with a pair of speakers built in.

Thanks. That may be an option for the future.

Anyone who tries to sell you stereo from a single speaker usually has a bridge between Brooklyn and Manhattan, that you can purchase from them cheap!

The problem with most keyboard amps is they are built to be loud, not high fidelity. As a keyboard player you require a full range, high fidelity system. For a little more money you can purchase a system that is a lot more powerful, high fidelity, flexible and true stereo. Today’s powered speakers are a dream for keyboardist.

From small portable PA systems like the Yamaha StagePas 600i (340W per side) or the StagePas 600BT (340W per side) 10 channel mixer, convenient setup and pack up.
To larger systems like the Yamaha Powered Loudspeakers

They start modest and continue until your dream sound is met. Compare any of these to the typical keyboard amp... especially the sound. High fidelity is the key. I think you’ll agree - there is no comparison!

No one is trying to do any such thing as far as I can tell. Some keyboard amps are integrated with two speakers supplying stereo without anything extra and some require a daisy chain of two single-speaker units to provide stereo.

For me, I aim fairly low for fidelity in practice (not that I want lo-fi - just that it isn't as important as portability and price). Although I haven't purchased a keyboard amp - I use someone else's amp at practice. PA at the gigs. And a pair of reference monitors (HS7) in the studio.

I do have all sorts integrated amp+speaker systems that are not far from the typical keyboard amp. Although I could have used that in the studio - the sound is not great and makes the keyboard less engaging. Prior to getting an S90XS a while back - I was OK with the run-of-the-mill amps. That S90XS piano sound didn't respond well to a clumsy setup which led to the studio monitors. I'd still use clumsy in practice since there's a different goal there.

And you have to also measure portability too. I've used a little 50 watt amp that's just over a foot square and maybe half a foot deep. It's pretty darn low fi but has gotten the job done in practice before I found I could plug into someone else's amp. It's not stereo.

i wouldnt recommend any Roland (KC-series) or Berringer keyboard amp to anyone that cares about the sound of their keyboards. We would need to know more about your use need to narrow to a specific recommendation: is this for live gigs - if so is it for primary sound to audience, or for your personal monitor, or both? If for home use, what type of volume do you want, how far away are you, etc.

To plug a yamaha product, For live performance sound I love their DXR series of powered PA speakers. Very rich, full, but also clear detailed sound with flat frequency response. DXR-10 or DXR-12 is my recommendation from that group. Lower cost / near quality is the DBR line. These are good, but not up to DXR level. These are both better than StagePas imo (others may find differently).