I hace a 5 foot Woods brushbull on my TC33D and am happy with the performance. I would not want to go with a 6 foot model, unless it is an area that is mowed with some regularity. If you let the grass/brush grow too high, it may be too much for your tractor with the 6' cutter... you might get through it, but you'd have to slow down to the point where it might be faster with a 5 ft unit.
I've been looking at tillers myself. My dealer has been steering my towards the 50" size range for a TC33D. I've not tried it yet, so no first hand experience... he said they may get one to use as a rental/demo unit that I hope to experiment with. If your soil has already been worked recently, you might be able to go a bit larger. If it's never been worked, you might have to go over it more than once to get it worked to a good depth.
John Mc.