"I know of 2 farmers around here that switched from a 8 row head to a 12 row. I have not seen where they gained anything. Now the cart and the combine both get full and sit wait for another semi and then do it again on the next load"

Been there done that! 

Use to run 2 - 8 rows and a cart.........THAT was a clusterF--- on the ends.    We get more done with one twelve and a bigger cart.   Yup the lands can be a pain, but a good cart operator (which we are VERY lucky to have found) can make things go smoooooooth!

We also though 125k is allot for a combine attachment!