i would get the sieve update kit for it and hopper extensions. also another thing to think of is on the intake boots on the chaffer sieve, they tend to fill up with straw and chaff. there is a part you can get from your deere dealer called an agitator which will prevent the build up of material
I have the hopper extensions and the sieve update kit. We purchased the machine from a soybean seed farm with 800 hours on the sep and they took really good care of it. We have been running a 7720 Titan for years and decided this year since the crops look good we would bite the dust and buy something newer to hopefully avoid those little break downs you have with older machines that cost you a couple of hours here and there during the peak times. I have no experience with Green Star so I will have to do some learning on that.
rotoary's love there horsepower, but I would stay away from the aftermarket chips we ran some and no problems but I know lots of guys that blew up motors. Sounds like you got yourself a good machine though with those kinda hours you shouldn't have any problems.
If you are combining any amount of cereals and canola, etc. (small grains), get an adjustable pre-cleaner. It cuts down the returns (which is often the limiting factor) and improves capacity. We had a 2000 model. I don't think the newer ones are different. We bought our adjustable pre-cleaner from Loewen I believe-not sure if you can get them from Deere.