I own the old school Peavey KB100 and 300. I like them both because they're built like tanks (rather heavy too) and sound really good for any keyboard. Also what I like about my KB300 is the EQ features. Has four inputs, and each input has its own individual input with low, low mid, high mid, and high (sweet for multiple keyboards/instruments). I don't own the Roland K500 but I have played through one PLENTY of times. Although you only get one EQ for all three/four inputs it still puts out remarkeable sound. I guess its something to think about. But these two amps are pretty much leading industry standards to my knowledge. At least I see them the most on the road!