My understanding is that the KX8 has the same keybed as the MM8 and the 61 key version has the same keybed as the MM6. If I had my choice I'd take the KX8 over the NP-30 for piano feel. The NP's keys really aren't weighted at all. It's more a "resistance trick" to them. They're kinda between semi-weighted and synth action. You get used to them fairly quickly though, but they feel nothing like a piano. Good inexpensive 76 controller though, but understand it's a very limited controller too.

If I had my choice of the KX8 or NP for driving the SonicCell I'd take the KX8 without question. It's a dedicated controller with more features and it's designed soley as a controller where as the NP's just a cheap digital piano with a few controller options that are secondary to it's intended use.., midi seemed more of an afterthought on the NP-30..