I agree pretty much with all the unbiased responses here. As for what Gary had to say, I also agree. Very well put, but with one addition. I recommend, if possible to test out the keyboards through the speakers you will be using. I have tested some both with headphones and speakers and found that it can sound real good through headphones and then trying the same keyboard through some quality speakers, it didn't sound as good. The same instrument I am referring to sounded much better using a Behringer UB802 mixer than just through the speakers alone.

Best
Scott
http://ScottLMusic.com