You've got several problems. If you buy more of the same crown from your cabinet company, you'll still have to deal with the gap above the corner cabinet. If you raise the existing crown to the ceiling, it's very unlikely you'd find unpainted crown that matches it's size and profile, plus you'd then have to deal with a gap between the cabinets and the bottom of the crown.

Here's what I would do. Choose the new crown mold you want for the rest of the room and measure it's height (how far down from the ceiling it comes). Make a mark on the wall at that height, then use a level to transfer that height to the stained crown and mark it. Then, trace the old, existing crown's profile onto the wall with a pencil. Now you have a mark where the bottom of the new crown will intersect the old crown, and another mark where the old crown will have to be narrowed to fit underneath the new.

Carefully remove the stained crown from the corner cabinet. Next, build a frame above the corner cabinet that's the same height as the new crown, and that extends beyond the cabinet to the point at which the new crown will intersect the old.

Now, install the new, painted crown around the kitchen and across the new soffit. Last, run the old crown through a table saw and cut it down so that it fits underneath the new crown.

With me? This is a tough one to visualize.

I would leave your cabinet molding as is, it is very nice.

I think in most homes, nobody notices when crown molding isn’t there. So I would not install the white crown (at least, not in the kitchen).

The crown molding on the corner cabinet looks stupid. It is sooooo close to the ceiling without touching it. Why in the world would anyone do that? The lower cabinets are understandable, but the corner us nuts. Any chance it could be raised to the ceiling? Is there enough cabinet frame behind it?

you will have to order #1 Tall filler, #1 Crown the same as what you have, #1 Scribe. ...all in the same finish and style to match the rest so the crown can go to the ceiling.