Houghy,
I own the Astronomiks OIII and UHC filters but they are only 1.25" not 2". The Astronomiks OIII is a superb deep sky filter, marginally superior to the Lumicon OIII IMO, the UHC is also excellent but I prefer the OIII marginally on several targets although realistically I think you would be happy with either. Downside is they are a lot of chaff, about $440 in 2" format.
I correspond frequently with Phil Harrington who writes for Astronomy Magazine in the USA and he rates the DGM NPB (Narrow Pass Band) filter as the best all round deep sky filter he has ever used and by a good margin.
The 2" version is currently available direct from DGM Optics for $US100 so you can land that for well under $AUS200.
http://users.erols.com/dgmoptics/
In case you have not heard of DGM Optics they are owned by a guy called Dan McShane and specialise in making high quality off-axis newtonians. I haven't used the filter myself but certainly respect Phil's judgement so that may be worth some thought.
PS: You could save up your chocolates and buy my 20mm Pentax XW which I am seriously thinking of selling
It would go well in your scope.
Clear Skies
John Bambury