The stock hangers (throughout the entire exhaust) are good. No reason to replace them unless needed for some odd reason. When I did my exhaust we cut off the stock hangers from the stock muffler and welded them onto the new muffler. We reused every stock hanger, worked good although took some time. In the future, I wouldn't do that again(cutting the stock rod off the stock exhaust), I'd by new rod and reuse the stock hanger points.
And yes, regardless of what anyone says, the catback IS a waste of money. It's nearly identical to oem. oem is stainless, mandrel bent, and sized appropriately. The muffler swap will net the same results as the cat back swap.
Really am not trying to upset people but it's just the way it is. The stock exhaust on these newer trucks is pretty nice. You still have a nice exhaust if you went aftermarket, it just wasn't necessary or any better than stock with a muffler swap(assuming you got a SS muffler and had a good shop install it. The only other benefit is you get the tips with the kit, I don't know how many people care a lot about that I know I don't but some do.
Breathing in and out is good enough for me.