OK, I've officially tried both (thank you, SweetWater). The Roland KC-990 was #1, simply too heavy. There is no way I could even lug that thing around - what were they thinking? Furthermore, it's sound was dismal. Sorry, Roland, just being frank. I just tried the Motion Sound KP-612S, and it is phenomenal, no complaints. The amp is VERY clean, and it will get one all the volume needed, the stereo is glorious and the tone does NOT deteriorate at high volume (I tried it playing with my live band, including acoustic drums, singers, etc.). However, I just returned it, because, if I put my Yamaha DXR10 speakers in the same physical location, I get the same results. And the Yamahas I can break into 2, 31-pound pieces. Although, I have to say, the 49 pounds for the Motion Sound KP-612S did NOT seem very heavy at all. I would've kept the Motion Sound if I did not already own the DXR-10's. I also have the Yamaha DXS12 Mark II subwoofer, and with either the Yamahas or Motion Sound, it's a very good piano sound. (I play a Yamaha MOXF8). I learned a LOT trying out the Motion Sound KP-612S: I've found that speaker placement is CRITICAL, and makes all the difference. So, if I'm not going to schlep around the subwoofer, then I need to place the DXR-10's properly, and they will compete (as long as I have a bass player with his own quality amp).