I have ST200 airbox and green filter, and aftermarket piping including the elbow to the stock turbo. Sound wise its still subtle but perfect for me. Windows down you get solid BOV style noises on throttle closing, not sure if it's very noticeable outside the car as I haven't heard it. I am certainly not snapping necks and subtle was the goal.
The piping and any sort of hybrid open air box but not "filter on a stick intakes" give a little turbo spool and BOV noise but not much. Enough to for me to be reminded what I have, maybe not enough to everybody else.
Maybe a little throttle response, maybe a couple horsepowers, these are sharpen and turn the car up to 10.5-11 mods. Relatively inexpensive, fun little day projects that round horsepower,
For me the OEM+ design and fitment, and arguably the best design for true cold air are the big draw to me for this type of "boring" intake design. Mountune and Cobb basically copied the design I think and in this case more plastic and OEM is good.
They hold their value well, if you decide you want more racket, re-sell and get a more open intake.