I've got a Magnaflow on my R/T and SRT-8. This makes cars 5 and 6 where I've used them and couldn't be happier with the results.
The Challenger took a couple thousand miles to break in (I've done <7500 in 18+ months) but if I drove it more it might not take that long. It now sounds like a Nascar ride when I start it up in the garagae and I get as many comments on the sound now as I do the car.
The Ram is more of a every other day driver and has started to break in rather nicely. I've got an '04 Titan with a Magnaflow and while its got a sweet sound there's nothing like the Hemi's with a kick-azz exhaust.
I got mine from P e r f o r m a n c e P e d d l e r (non sponsor vendor) for under $525 shipped. My Midas center has done all my exhausts and put it on for $95. The Titan cost more to install as it wasn't a dual pipe to begin with so a little work had to be done.