I bought the ART pipes first and then was looking for either a Cobra non-res or Buddyclub as I was after impact I ran a non-res with stock cats on my DE before my HR so went with that again in the end.
With the non-res my setup was a little raspy between 2-3 but that's what kept it drone free in that zone, the resonated mid pipe probably would have improved the sound but it would have lost some volume which I was keen to keep, above 3 it opened up nicely and howled at the top, the idle was exactly like valy says, deep and aggressive.
My HR would completely drown out my friends R34 yet his droned like crazy inside.. as I said before I could not have been happier with it. Nice and loud but silent inside when needed - oh and as with normal decats full gunshots when on the pop/bang map.
Compared to how normal decats sound on a non-res cobra (horrific rasp-fest) compared to how mine sounded, that probably shows best how much ARTs do to help. I'm sure on a usually deep tone exhaust like the buddyclub it would sound unreal!
Reminder though - These ones are for an HR & 370s, will not fit DE