Interesting that HammondSuzuki marketed the XK-4 nearly the same way as the Xk1c: “2 or 3 updates to Leslie/organ sounds” which the SK-1 was never able to get in its updates. From what I can tell they were very subtle changes, most probably being along the lines of: “Heh, I can change the Leslie mic from a Shure SM57 to a broken Shure SM58. Lol cool.” When I bought my SK Pro (61 keys, used for a fair price) I definitely thought: “Oh, I bet HS will do that again.” …yup they did that again (I guess Nord, Apple, Ford, Toyota, ….heh, even US Presidents are just all slight updates to the previous entity).
But really in the end those SK-1’s still serve a great purpose for organ work. It’s not like my SK-1 suddenly sounded “bad” or “ehhh decent” (no one’s saying that, but I feel like maybe it’s implied) with the XK1c’s out in the world. Who in the hell really can hear these 0.2% differences out in the wild? I’m sure if I was recording organs, the XK1c (and now the XK-4) will be 0.2% more believable to the listener with headphones. I’m sure the update is a bit more significant from SK Pro to XK-4 than SK-1 to XK1c but I doubt I would be just blown away if these were side-by-side (the extrabutton/knobs and dedicated overdrive knob is a sizable upgrade).
…I really should MIDI up my SK-1 with my SK Pro before I offload the SK-1 to compare Vox, Farfisa, Pipe, pianos/EP/clav/etc/Leslie …I don’t really have the video capabilities or nice editing abilities, but do have a decent recording rig.