<font color='#000000'>I think you would hear a definite improvement over a standard HTIAB system, but I wonder if the improvement would be large enough to justify spending another $500. For the cost of your original system plus this one, you could put together one that would outperform either one by a long shot.
My best advice is to take your time and listen to a lot of different setups at different stores, including high-end audio stores and setups way out of your budget. I think this will give you a better scope of your choices and eventually lead you to a well-informed decision that you are very happy with.
As far as the MTX goes, I've never heard of them. Having a certain size driver (10" in this case) isn't necessarily good or bad for movies. It matters more how it sounds rather than how it's made. Maybe all your testing will lead you back to the MTX after all!</font>