Hey mate
Depends on what you mean by noisy. Some of them aren't really loud until you stomp on it otherwise they tend to just have a bit of the burble or light drone and that's all. I have come across a gen5 or two in WA which appear to have had fujitsubo or HKS cat backs / TBEs. TBEs will of course give you the most out of the system although the dump is where most of the gains would be in theory. From the JDM ones it depends on which of their specific models you go for. As for the local ones - same thing you need to check. Personally I just went down the JDM path. Less hassle lol. But that's a personal preference. From memory some of the gen5s in Sydney have gone down the full TBE setup with the above brands.
Matt (KiDo) advises against wet filters fr memory so all I did was to buy a hks panel filter. Slight sound that's all. (Would love more than that but!)
+1 for the xforce dump - quite a few cars here run xforce dumps from memory (gen4 and or 5)
With the gen4s a few of us changed to a 3 port boost control solenoid. Not sure if that's the same recommendation for gen5 so I would give that a check with Matt.
Exhaust shops - as mentioned by jslayz. I have used Mettams at morley - great bunch to speak to - pat, Julian or Ian.
STechnic can install if you supply the parts too. And they probably could recommend a few options.
I'll let the other WA boys chime in