Why are they so expensive, do you get a sports cat with it?Is it from the turbo back ie includes a freer flowing elbow?
There's no way I would pay £1000 for an exhaust.Just go to a respected exhaust builder and tell them exactly what you want.You can pick how many boxes you want and the type & size of them so control the noise that way.
I used to have a 2.5" on my car with a 3" Janspeed downpipe.I had the rest of the system made in 3" with 2 silencers and a smallish back box, costing around £450.
It was quieter on this setup than the last and immediately highlighted how much back pressure the old system was causing as the car immediately spooled quicker and pulled harder.
It's not like Miltek will have some magic formula for the exhaust, chances are they will follow the same path as the original, just with mandrel bends and decent silencers.