To get the most from the performance of the car you would need the downpipe with the sports cat. You can go with either a resonated (quiter) or non-resonated catback section depending on your preference for noise.
You could also go for the APR RSC exhaust system, which is a little more than the Milltek, but I thinkhas a better sound quality to it.
There is also a Blueflame option, which is slightly cheaper than the Milltek and has good reviews.
