From my experience...
http://www.zax.com.au only really deals with companies, not individuals... but if you ring up sounding like you know a bit of what you are talking about, he will deal with you... he is expensive for PCBs and generally, only has second hand parts... no new.
Bumper is a little better as they target the home market. Again, not cheap, but does have some good stuff. Parts wise, not sure what he has to offer. I purchased a cocktail cabinet from them about 4 - 5 years ago... great nick... couldn't resist... they are a bit shonky with customer service from my experiences.
www.240.com.au is probably the best I've dealed with. Deal more with pinballs, but he also import cabinets. Prices are quite fair. Plus they also deal with the home based customer. Dont stock much new arcade parts though.