The difference between the two are horsepower, final drives and hopper size. You could order heavier final drives on the 9650 STS.
I personally ran both 9650 and 9750 STS on the harvest run (02 and 03's) and there was no discernable difference between the two in the wheat. If you are in need of the extra hp, I would go for the 9750. There may be performance chips to boost the 9650 (I know they were available for the 00-01 yrs)
I know someone else will know!!
We ran them side by side in the corn and beans too, and once again there was no difference in the beans, but we ran different size corn heads in the corn so I can't help you there.
Mat if you guys are needing to go to 2 bigger machines then you need to look farther then the 9750, I don't know that 2 of them will equal 3 9600's, it will be close but if you are pushing to finish with the 9600's then you may want to go one step larger then the 9750.
If you are looking for the best bang for your buck I would consider looking at some different color options, I think the gleaner R75 is a good value choice, very simple design easy to work on, and those things will eat up a crop in a hurry, we run 2 75's and a 72 right now and love them but we are getting bigger next year so we are going to lexion which is also a great choice for heavy duty machine, my opinion top of the line combines, but you probably need to demo a few different machines to see which one works best for you.
we did demo a new holland CR940 and it was great for capacity but broke down 3 times in four days, our 9600's flew right by him when he was sitting and overall got more done.
as for caseIH neighbours have then and say they are hard on fuel with those cummins engins and also break down a lot, i am staying with green.
We used to run 4 9650 walkers with 30ft. heads and upgraded to 3 9860s with 35 ft. heads and we have actually been able to do more with the 3 98s than with the 9650 walkers and also eliminated a extra operator. It was a great change and I would reccomend it to anyone. Our 98s have performed very well except for some minor problems. I would reccomend getting a newer one with the bubble air intake as that made a huge difference in how often we had to blow out the airfilters. I don't know what kind of head you run but the 635 is a great head we only had some feeding issues the first year they came out but ever since they have been really great.
Do you need to buy them now? Txfarmer put a post out a while ago where there was research saying that Jan-Apr was the best time of year to buy $-wise. I found that prices seem to be $20k higher now than winter time.
I guess I need to read the posts with a little more care, skimming doesn't cut it I guess!! It might've been kinzepower, but our dealers have been known to "stick it" to guys who buy just before harvest. The sticker/retail price on used combines may stay the same throughout the year, but the salesmen may swing a good cash deal, or other incentives when January rolls around. They don't want their stock to start having birthdays on their lot!!
We've been looking at used combines and the price set out for them seems to be much higher now at harvest time than when we were looking in the winter time. That's just our experience.
I don't know if you are wanting to go from 3 to 2 or 3 to 1 machine. I'll go with what looks like you're indicating 3 to 2 route. Here goes in reference to what you have now. Used to run 3 machines ourselves. We recently bought a new 9760 to replace our two Case IH's and I got to put 100 sep hours on it this fall already. Heres what I have found:
I did some custom combining soybeans (800 ac ) for a local neighbor that has a pair of 9600's. He has 930's and I had 635 on mine. On each quarters, I consisently did 80+ acres with my 9760 to their barely 80 acres with their pair of 9600's. This shows me that the 9760 will do the job of 2 9600's guaranteed. Now, if you were to get a 9650sts for a second machine, you would more than succeed your objective of going from 3 to 2 machines while doing the same job and then some more. We also have a 9650sts and it has more capacity than a 9600. We used to have a 9600 before switching to the 9650sts.
As for going from 3 to 1 machine, I can't really help you there as I cannot tell ya what to do.