I've never used a B3200 before but I'll say this. My L3000 weighs (with fluid) over 1000 lbs more than a B3200 and with a full load of dirt my 66" box is all mine wants. Sure I could handle a 6' and just take a smaller bite but why. I'm not going to say your tractor can't handle a 6' box but I don't think you can get 100% capacity. I believe you'll loose traction before you max the box out.
It isn't power you are lacking. Traction is what will get you. For traction you need tire size, and weight. You are a bit short of both.
Just by the way, I was down at the dealer roaming around today, and I really like the looks of that B3200. Nice machine!