Hey Midnight,
lilcrash has the right idea with the bellmouth dump pipe down to the cat, youll get a better spoolup with less restriction at the wastegate.
Your other option is to keep looking on justjap and get a shortie split dump for about the same cash. the split pipe then needs a dump down to the cat.
The benefit of both these is the wastegate gas and the waste gas dont get confused and bump into each other near the back of the turbo.
I'm not looking to start an argument about which brand as many people are partial to type, some manufacturers make claims which are true to the specific test subject setup they use in their product development with regard to power outputs at rpms etc.
I dont have a dump pipe yet.
Mine has a magnaflow cat (i know there are better ones out there), the rest of my system is a custom built 3 " with a jun spiral on the back, we can catch up and i can show you how simple it is if you like.
Any reason why stainless other than it looking cool?
If all you want is a change in note on your stock system, take off the rear muffler and put some straight pipe on.
Or, get the catback on and save up for the rest as you go if all you want is a nice note with an improvement in flow.
Any way it goes if your system is straighter and has a greater diameter than your stockie its an improvement.
Do the sums on parts and then find out how much for fitting it. (the last thing you want to do is snap a bolt on the back of your exhaust housing)
Go somewhere quality for the install / build, ie Everlast at the gully or Exhaust Technology at goodwood.
Remember your car will drive differently and it will take a little time to become accustomed to your car's new feel.