I've got cybox short tails on my 370z at the moment, cold start up its very loud, but once it warms up I'd say only slightly louder than oem. This exhaust screams at WOT, I get a few burbles if I go over 4k and lift off throttle.
I've done a few longer distance journeys on the motorway and sitting at 70 in 6th there is virtually no drone.
Loud but not to invasive