The best option would be to run a 6.00" round can on a custom pipe and no rear silencer (sound balance is better the further up the car the silencing is employed).
Alternative would be to fit the Milltek but again leave out the milltek back box and avoid the need to take the gasses on 90 deg - 180 deg flick through the rear silencer.
This set up up will sound the best with out making you sound like a tractor and also benefit exhaust gas speed when remapping for big power.
Cheers
Nige