Well here is what you don't wnat to hear...
Exhaust wise anything forward of the catylitic converter will void your warranty, therefore a
TBE will void your warranty. Cat back systems offer minor performance gains.
Tune wise, VERSO is best bang for your buck.
You will find that workshops will offer you a better price on work done to the car if it is all done at once.
The other advice you will hear is if you are worried about warranty forget about modding mechanically, unless you have the time and money to keep swapping to stock parts if anything goes wrong with your car and needs to be sent back to the dealer.