I think the shrouded model of the O/S model Wildcat would still be mousefart quiet compared to what is delivered to us here in Oz. Silencers are a prohibited item but if you want to do all the paperwork and comply with the rules& regulations associated with a prohibited item then you can have a silencer I believe, but for the average Aussie shooter it is too difficult to be bothered with.
Paulcat, I should be able to answer your question regarding noise from a FX500 in a week or two, I am waiting for mine to arrive, it will be regulated and I am guessing it will probably be as loud as my Huntsman .22 at 40plusfpe before I detuned it, think standard velocity rimfire loud. Where abouts are you in Oz?