Mine is not a full cat-back, it goes cat-> 1st resonator-> 2.5'' piping to Y split, to two straight through ebay mufflers. Did not have much to spend on it, cost me only $240 total (2 mufflers and piping/installation). I think a downpipe would finish it off well. (i dont want too loud so tp could stay)
3000GT sohc custom cat back exhaust clip - Video
I definitely need to get a WOT to redline run to actually get the sound. In vid its only to ~3k.