I like the Magnaflow systems. The sound, quality and competitive price of their systems make for a best buy IMHO. The sound is not obtrusive in the cabin, quiet down the road but definitely a great sound when you get on it.
I had Magnaflow on my '99 and I have it on my '06 300 SRT8 and the '07 Hemi Ram.
I've noticed that the Borla systems sound very much like the Magnaflow systems.
The Flowmaster systems are just a bit too loud in the cabin for me. I like to hear the music.