The biggest thing every one on here is going to tell you is to get rid of the DPF and Catalytic Converter. You'll need to get some tuned software that will allow your truck to run without it. If you just put a different pipe on there, your truck will throw a fit. Aside from that, you might want a better intake. With just an intake, tail pipe, and DPF/Cat delete (with the appropriate tuning) you can be pushing 500 HP to the ground, and great fuel mileage to boot.
What you have to do though is keep all that exhaust pipe and DPF/cat in case you have to do any warranty work. You'll need to put it back on most likely. Unless your dealer is really cool, and is okay with it. Most are not. Likewise, you will have to put the stock software back in the truck before you take it to the dealer.
I'm sure the venders will chime in in a minute here and reccomend a set of products for this. The intakes are pretty much AFE and S&B. Both are good, S&B is a little cheaper. DPF/Cat delete pipes are available from a number of companies. Powerstroker67 makes a nice one. I run that one on my truck. And for tuners, there is Spartan (my favorite), SCT with innovative custom tunes, and apparently a new Edge with DPF delete option (it's brand new, and i don't know much about it). Edge is considered to be a less-than-ideal product, and i really wouldn't reccomend it.