Milltek are a ripoff IMO.
A good exhaust place will make you a system that sounds exactly as you want it.
Best way to ensure they're upto the job, is make yourself a decent spec list before you go in, do your own research, and ask them about each item in detail. For instance you want proper mandrel bent pipes, and you might want a particular bore. The **** places will usually make excuses and say X,Y or Z is better, ie "oh you dont want a 2.5" bore, you'll lose torque, what you want for your engine is a 2.25" bore as that will maximise torque". They also tend to build the system on the car in such a way you end up with one huge long unmaintainable lump, rather than having joints in the exhaust so you can remove sections for maintenance. You need to be able to recognise the BS and lies that they might come out with. The good places will supply exactly what you want, for much less than milltek will bone you for.