Sorry to revive a somewhat dead thread. I just had the Ark system installed with Berk HFC's. Sounds absolutely stellar. Sofa King is not joking - the thing sounds mean down low and like a race car above 4,000. It's really awesome.
I do have a bit of "gurgling" at 2800 and less when engine breaking - not sure if that will go away when the packing burns off or if it's normal. Sounds kind of odd but not bad.
As far as power goes, it absolutely feels smoother all the way up and a bit faster. Not sure if it's just me being biased because it sounds awesome - but it's great.
Very happy with this system
. It's quite loud with the HFCs but not obnoxious or ricer-like.