I have Berks waiting for me at the shop. It will be paired up with Nismo CBE. I have not heard any Berks with the stock exhaust. From what I remember the sound for Berks HFC is:
HFC w/stock exhaust = 4
HFC w/Nismo = 6
HFC w/Berk CBE = 8
Minicobra1' first post explains it all. Good write up. HFC's are the best bang for the buck!
Sound clip here:
Berk Exhaust Production with X-Pipe