Yeah that's pretty much true, but jet's audio is pretty close to what they sound like (very good videos jet). The sound files I've heard tend to not show the bass as much as in person. But, the clips can still be useful for comparison sake.
What I looked for when I was listening to sound clips while making my choice was not just how much bass the muffs put out at idle, but how deep they sound revved up (I think how they sound revved up is critical if you want to sound like a big block under power). For example, listen to jet's car then listen to a magna sound file when they rev it up...the magnas are only slighty quieter at idle, but the MACs are much louder at WOT...and it sounds even louder in person...the MACs sound bad a$$! It's probably because the Magnas are straight thru muffs...also, they don't tell you this, but the straight thru muffs actually decrease their diameter a little inside the muff before the exit. This helps create a slight amount of pressure and turbulence to push the exhaust into the little holes on the sides of the pipe inside the muffler to muffle the sound. I think that design also knocks down a little more bass than the chambered type as well as the high notes...that's why a chambered muff has more bass (and sounds better with an H pipe) but why straight thru muffs sound better with an X pipe (not as raspy).
You also have to consider how much drone you can tolerate. MACs do drone. The more bass a muffler puts out at idle, the louder that drone frequency will be at 1800 to 2000 rpms...it's the price we pay for trying to sound like a big block with 281 cubes. I would still rather have chambered mufflers than straight thru since I like it loud, but it's not for everybody. If you can stand the drone, the MACs are nice and deep, loud at WOT and look cool too. Lifetime warranty too I believe. If you don't want drone at all you will want straight thru muffs or Borlas or Corsas. The choice is almost endless on these things, but research your butt off and you will find what you want.
06 Stang GT, Yeah I got stuff! Check out my profile for the low down.