Well from what I've heard, of any combine produced, the 8010 should be the one with the ability to get the most HP to the header. Many combines use a set of belts to drive the header, while the 8010 uses the PTO style shaft to drive it. This allows for more HP transfer, without the issues of belts slipping.
When you get into an 18 row corn head, that is a lot of rolls to keep turning. If you run a stalk chopper too, thats even more load on the header drive. The taller the corn is, the faster you'll have to spin the rolls, so you would need more HP there too.