I agree with you all on here about the full finger auger. However, I think that if you really want performance with a flexhead in soybeans an air reel should be something to consider. We went from a JD 930 without full fingers and no air reel to a new 930F with both. I rode with my buddy in his combine with a 930 full finger (and no air reel) and I thought it was better than without full finger, but ours with an air reel was considerably better even than his. The air reel pretty much eliminates all bunch feeding (even in "tough" conditions) and shatter loss over the sickle. About 6 or so years ago the Crary air reel was about $10,000 or so. I think it was one of the best inverstments we've ever made in equipment...it saves beans and wear on the machine (and operator!) from slug feeding. I think it's safe to say you could add .5 to 1 mph of harvest speed as well most of the time with the air reel. It is now a rare occasion to plug the feederhouse on our 9610 combining beans.
As far a sickle goes, years ago we ran Tiger Jaws, but for the last 15 or so years we have just run the JD factory sickle and have been satisfied. When JD came with the corse serrated edge sections we've ran them because they last longer. Have considered a Crary sickle, or something else maybe, but havn't spent the money yet.