I'm going to have to offer a different opinion than tony - I've got UEL headers (OFH), Perrin 2.5" catted/resonated headerback. I can hear my farts fine in the back
Seriously though, I'm pretty sensitive to noise (I had the Evo3 catback before and had to sell it as it was obnoxiously loud to me, even with silencers). The Perrin system I have is pretty damned tame, the OFH gives it more bite, and you can tell the damned thing has aftermarket headers, but it's still nothing I would consider obnoxious. I could actually go for a bit more if I thought I could without going overboard.