its all very subjective. I've had an arc grip fitted for a couple of weeks which replaced my cobra cat back (will be going in the for sale section when i get round to it), and too be honest I've found the arc a bit too tame coming from the cobra, which sounded great but i think would be very loud with HFCs.
I've since picked up a set off second hand berk HFCs off ebay for a steal to try, ill let you know my opinion on them.
Point is there is not one setup to suit everyone which makes it very tricky.