if your not worried about internal speakers the SD1 is the better keyboard, but I do like the X1. You will be pleased with either after having a KN1000.

If its for home use, Ketron doesn't sound great through normal lo-fi keyboard amps, you really need an amp that would sound good playing audio CD's

There are loads of goodies available for either keyboard too in the form of styles, extra sampled sounds and hardware upgrades.