The Powerflow pipes are custom built for every car, they dont just make them up in a factory and ship them out, they are measured and built on-site to exactly fit your car.
I had one made for my last 5 turbo, a side exit, and I must say I was very impressed with the build quality and fit and the cost. So unless they have gone up in price, they were almost £50 less than any other make, and the sound was lovely.
I suppose its all down to personal experience in the end.
Basically, you tell em what you want fitted and they make it for you. Simple.