Worlds latest reply but I ended up going with a set made by Infernofab, these are the only direct fits I could find on the internet except for some discontinued Borla reps I found popping up now and then on ebay but they looked pretty ghetto. the infernofabs are quite pricey especially getting it shipped from the US to AUS.
You definitely can fit some 2.5rs or even wrx headers but you will need to pretty much get a full custom J-pipe which could be funky.
I am yet to put it on the car, but they bolt directly onto post facelift (~06+) 2.5i's (and maybe 2.0rs????) and for pre-facelifts like mine you have to need to buy an adjustable J-pipe (infernofab sells one without the cat which shouldn't throw a CEL as the rear o2 sensor is relocated onto the header (post-facelift design)) or buy a post-facelift J-pipe and have an exhaust shop shorten it a bit as well as buy a rear o2 sensor extension. This is the route I'm going with. The quality of the headers themselves are insane, welds are top notch and they got a wow from my machine shop when I got them coated.
This is the infernofab uel header (heat coated) with a cat in it like a post-facelift header, it ends next to the exhaust flange, if it were to suite the pre facelift J-pipe it would need end earlier, about in the middle of where the cat is.
Seemingly the rarest photo on the internet, this the stock 03-~06 pre-facelift header and J-pipe. They connect in the middle of the header, instead of next to the exhaust flange like the post-facelift.
This is the correct post-facelift J-pipe lying next to my pre-facelift setup. The post-face lift has only 1 cat in the J-pipe and is a bit longer then the pre-facelift so it would need to be cut down.