Had one built for my Saab Turbo about 3 years ago (downpipe back) Instant power increase, and wonderful sound, nice and rumbly through town at low revs, but wailed like a banshee when revving it hard. Turbo lag eliminated completely. Absolutely beautifully made, with some real expertise.
Plus it dId away with the cat with a bypass pipe. Come MOT time, just swap them over.
And the price is very good-system will last for years, and always put a smile on your face. Why go to Kwik Fit when your standard system goes-spend the (very little) extra and get a proper exhaust