I fairly positive they are stainless, and I think the warranty is a 1 year warranty if I remember correctly. But, if I were you and I wanted the best sounding mufflers for these cars, I would just buy these and never look back. As long as you stay out of it these stay pretty tame also, so driving around town isn't an issue. And the money issue, I don't believe I have ever seen them on sale and I wouldn't expect them to, but you've gotta pay for the best I've found out...
Black 2011 V6 - Totaled
Candy red 2012 V6 - Sold
Candy red 2013 V6 PP - SCT tuner with Jon Lund tuning, BBK TB, FRPP Sport Axlebacks, Airaid CAI. SOLDDDDDD
2003 Redfire Terminator - Too many mods to list, SOLDDDDDDD
2012 Yellow Blaze 5.0 - M6, Lund tune, GT500s, O/R H pipe, and some other cool stuff