Not sure if you have zircotec available to u in 'straya, but i was in charge of the exhaust for the race car and it was sent to them to be done. Ours was done in their standard creamy kinda colour but they offer a full range of colours. They sell gold reflective sheeting for the intake which i'd probably be more inclined to go for, mainly because u may find urself changing parts of the intake system if not the whole thing itself. It'd be easier to recoat the intake in gold sheeting as opposed to ceramic coating.
Just to give u a rough idea about the 3.2 battery set up
VWVortex.com - DIY: Battery Replacement A3 3.2 Quattro
They make excellent products.....we used a lot of their sheeting around the hot side of the engine on mine,to shield things like the diff,and some of the piping runs.
I didn't coat any of the intake and to be honest,thanks to the WMI and ProAlloy intercooler,we don't have inlet temperature problems,and even under load it will sit a few degrees above ambient,prior to the WMI system.
It may well be a worthwhile addition if you didn't have all of that,for sure.
The rear battery well does have one other very good use.....the WMI pump is down there on my car!