I'm in the same boat, looking for an exhaust to mate to the berk HFC. I've been looking around and found that the invidia seems to sound pretty decent. Below is a link that I've found...also below is the link to the guy from guam and his berk set up. The berk is nice but pretty pricey. The invidia can be had for several hundred less.
ERZ HFC's and invidia:
YouTube - 370z Invidia Gemini Exhaust and ERZ HFC review
Berk HFC's and Invidia:
YouTube - 370Z Nismo - Invidia Gemini CBE & Berk HFC's - #1
Berk HFC's and cat-back:
YouTube - 370Z Berk Exhaust