Shane - I was talking to Mat at the Perth show and the TX6 has a different wheelbase, the wheels have been moved forward slightly to balance the bigger front box. Plus the batteries are now under the camper near the axle, not on the drawbar. This also moves weight off the drawbar. Point being, I don't think you could retrofit the bigger box
Hogie - you may want to consider the hotplates and sink for the kitchen. I never had it on my Camprite and at the time prefered it that way. But after having a "built-in" sink and hotplates with my Quantum, I wouldn't be without it now. I thought I would lose benchspace on the Camprite with the sink/hotplates and so was happy with the portable stuff. But what happens is you end up losing the sidetable to the gas stove and plastic sink, so either way the space is gone - plus you then don't have the convinience of the inbuilt kitchen and its ease of use. Anyway, just thought I would mention my experience and how I would do things differently second time around.
Cheers
Captain