If you have that kind of volume to move...why aren't you simply hiring your local grain hauler running superBs if you want a lower cost solution? I understand wanting to do things when you want and such, exactly why I have my own, which is only a tandem, well actually an A train in fact, of which I no longer pull the pup as a unit except on occasion. I am hauling similar distances for local deliveries such as canola or local feed markets. But in no way, when moving larger volumes, or having to travel further yet, can I come close to competing with the cost of what my local trucker charges. I'm burning almost as much fuel and putting as much wear and tear per trip, and it takes me just as much time to haul 23-25 tonne as it takes him to haul 44. So yes I haul my own when I can ship locally within say 100 miles if it's only a few trips, anything more distant or on large volumes, it's hired out. I just can't run my own truck for what he charges, but of course, things are then at his convenience as well, which I don't really care for. But it all comes down to dollars in your pocket at the end of the deal.
If you want to maintain your freedom to do as you please, which I can completely appreciate, my advice would also be go with a SuperB simply based on volume and distance.