Very important! The explanation linked above makes sense and I recall the first time I witnessed an M4 in traffic. Oh wow an m4, rolled down my windows, and complete disappointment! That said plenty of twin turbo cars sound great but for whatever reason the S55 sounds thin and ricey no matter what you do to it. Some people love it some hate it.
Simply put the S55 can sound aggressive but never sexy! The n55 in my second 135 below which was only catless DP and stock axle back show how great the N55 can sound!
WARNING AURAL BLISS
https://youtu.be/wLZNSJv6a3U?t=40s