Depends on what model you get. I have 50 Series Delta Flos on my 360 powered Barracuda and they have a nice rumble while cruising with no interior resonance, the WOT sound is very authoritative but not objectionable.
The 50 Series Delta Flos aren't even the quietest muffler they offer, there are two series (30 and 70) that are quieter and the 50 Series SUV muffler I had on my Dakota was no louder than stock at cruise and woke up at WOT.
