I've had a HD8, a HD10 and an 860hp Earthsaver tub. The duratec machines are good, but my HD8 had a 300hp Deere in it. I would say a 100hp model would be painfully slow. They are horsepower hungry machines, thirsty too. What sort of $$ are you looking at spending Willy?
If you do go the grinder route, I would ditch your chipper and buy a grapple truck to do your jobs with, and batch grind all your waste.