The CR has variable speed V-belt drive for both the rotor and the feederhouse. If you open the side shield on the right hand side of the combine you will see both large variable speed drives. The rear one goes to the rotor gearbox and the front one drives a jackshaft that runs across to the left side of the combine where the feederhouse hydraulic clutch is. The clutch then drives a 4 or 5 band V-belt down to the front feederhouse shaft.
You can run a 12 row head on a 940. If your looking at aftermarket chopping heads they do use more power. You would want to have the optional larger 70MM lift cylinders for the extra weight. The standard 62MM cylinders do good with a 12 row 20" head. I'm not sure how much more a 30" wide head weighs.
As far as price I only know for cetain what a guy near me paid for his. His is a CR940 2003 model with planetary final drives, RWA, long unloading auger, fancy cab, yield monitor, 300bu hopper. His was right at $220,000. He farms about 600 acres and milks cows. He said he figured he should get 15-20 years out of this one.