I'm using a Roland KC 550 amp with my PC3LE7. As best I can describe it, My piano sounds are "muddy". It sounds like there's a light blanket over my amp. But when I practice with headphones on the piano sounds are good with nice clear, crisp sounds. I've played with all of nobs on the amp but nothing really makes an improvement. I've tried playing with the patch setups but I can't see Kurzweil putting out a product that would need such tweaking out of the box. Is this a hookup thing from keys to amp? A stereo vs. mono thing?