I don't think I could ever forgive myself if I got a four string version of my bass. Every time I consider buying a four-string, I'm messing around with one and I'm looking for the low C or D and I toss it aside. Traben accomodates that low B so well.
How about a six-string Traben? The neck would be ginormous.

Also, the Kore four strings are, oddly, 35"
I would all kinds of buy a Traben 6er, btw.