I think they sound too high pitched. go to mustang exhaust .com's forums section they have lots of sound clips you can hear for yourself. your good with magnapacks you have plus they outflow slp's
Some people on the Registry really like them. I went with the MangaPacks for $315 to my door from Performance Peddler. I would like to order the rolled tips but I haven't yet.
They sound great! I think they have the perfect Muscle Car sound. They are loud at WOT but can be kept quite while crusing. I've heard sound clips and they do not give you the effect of what a sweet sound the SLP's put out in person. My Son has them on his GT and they sound great on it too. But the 4-valve Mach makes the SLP's talk even more with a much louder tone and NO rice, rasp or drone!
They are straight through design, similar to the Magnapacks and are actually resinators, not mufflers. I love the Magnapack sound too but elected for the SLP's because IMO they can be real loud at WOT and still be kept a bit more quite while crusing than the Magnapacks.