I found that with a 8 row chopping head I needed more power, especially unloading on the go. The combine was running around 2150, and if I was not pulling back slightly when I hit the unload button the rpm alarm would go off...oooops.
I forgot to add, this is with a 9760, the 70's have more power and we have not had it in corn yet. Hopefully at 5.5mph it runs over 2200rpm with the chopper head.
Also, last year we were using a Harvestec and now we have a 608 stalkmaster. The Deere seems to bring in less MOG so that should also make things run more efficiently and use less power.
I wish we had the pro drive that will come on the 2010 model, at higher speeds with an 8 row there is significant power being wasted just propelling the machine across the field.
A 12 row is far more efficient in this aspect but there several logistical issues that arise with a 12 row.