Donny:

I don't have a lot to add except that you probably know I've been playing a Hammond SK2 for some time now (3+ years). I absolutely love this keyboard and wouldn't trade it for anything. It has the real Hammond sound, although I agree with Bill Lewis that the tube preamp of the XK1c sounds warmer than the SK's digital tube preamp sims. I sold my XK3c to get the SK2 and have no regrets.

One trick the SK's have is that you can assign an EP or AP or other sound to the bottom keyboard and organ to the top (SK1 can apply different sounds to the L/R split)... I don't think the Nords can do that nor even the XK's. And you can download extra sounds to the SK from Hammond too which the XK's can't. The SK's EP's, both the Rhodes and Wurli, are staple sounds at my gigs. So I just carry one dual-manual keyboard to my gigs and use it as a multi-keyboard rig.

I think the best thing about the SK2 is that it has a small footprint on stage yet it's a real Hammond, and that makes a difference in the way it is received by the audience and my fellow band mates. I know of an instance where a jazz organist in Atlanta advertised himself as a "Hammond organist" and he showed up with a Nord - people complained! I highly recommend the Hammond SK1/2.