OK so i bought my MY06 a couple years back and when i got it, it had a horrible exhaust which was essentially a 3" pipe from turbo back with a cheap canon muffler on the back... it was ridiculously loud.

I drive a lot and wanted something quiet, so I put in the standard exhaust from an MY07 STI... but now i am thinking it's too quiet and i wanna try and get a little more power... but my thoughts are to change the headers, turbo and dump pipe, but leave the standard cat-back... (obviously get a tune to go with)

So my question is, has anyone done this before? will it work ok? or am i increasing the flow and then leaving a brick wall at the end of the exhaust?