I agree, I have considered this option myself as this car looks awesome with the 17" and black duco . The only thing you will have to keep in mind is resale as your base XR6 will return better money over a couple of years. If you plan to keep it for a while, it shouldn't be a problem.
As for performance I have heard that the 220 5.4 should respond well to an exhaust upgrade but the system may be expensive due to the difficulty in fitment (seen the cramed engine bay??). If you do it in stainless and add a performance chip sourced from the USA, expect to raise the performance by 20-30kW's with one hell of a torque pull. In auto form times may come down to the low 14's. In manual it may be a different story and more fun.
Thing to keep in mind is by now you spent the same as the XR6T, which bar the awesome V8 grunt, would be a better car choice all over....dam.
The best buy IMO is the same XT as mentioned above with the 182kW and all the mods. It doesn't cost as much, looks the goods and will still go like the clappers.
WASP GT - Mk2 6 speed + Herrod =