I just installed the ADT 4" system
I got the 14ga, no muffler, system with a 5" rolled stainless (pre-welded) tip for less than $500. 00 (shipping included). The hangers were welded on, but I had to beat the crap out of the one that goes on the transmission, because they mounted it about 1" too far forward.
I'll post the whole story plus pictures in a new thread soon. Other than some of the installation problems, I like the system. Has a little drone at 2200 RPM, so I will put some dynamat on my rear wall and floor.
Even with problems on install, the whole job took about 3 hours by-myself. I don't have a torch.