I like to "build from the ground up " too. If I were to replace one of my two boards., I'd no doubt keep the Motif ( stunning sounds and great for techno / ambient stuff ) and I'd part with my PA80 ( arranger with excellent sounds and synth editability but also with some limitations that I don't like ). I'd go to either the Triton or Karma instead.

The 9000 is a great board / arranger and my limited experience with the 9000 pro tells me it is also a great araranger. In my own case though I don't necessarily need ( or want ) an arranger though for composing, especially when I consider that I already have the arranger like features of Jammer Pro, XG works, and Sonar's Musiclab drum and guitar accessories, not to mention a few others, even some useful freeware apps.

Another way to look at it.. for approximately the price of a new 9000 pro one can purchase BOTH the Motif and a Triton Le or Karma.