Although I think you can get a slightly better sound from the XK3. I think the VK88 is a good model. Almost all the organ clones sound equal when you play them through a leslie. The difference usually comes in the bass, on some the bass, when played through the pedals isn't as deep as a normal organ. This isn't the case with the VK88 as it is with the Korg CX3, which is why I want to switch. I'm getting an XK3, and may use my CX3 as the second manual for it. I don't know yet.
If you plan to get a VK88, also plan to get a good leslie or leslie simulator, like the Motion Sound Pro 3T, since the VK88 doesn't have a tube in it, the sound isn't as distinctly Hammondish as it would be if you played it straight through an amp. If you plan to just play in the background, you may not have a problem though.