can you please tell me where the best place is to purchase a 100cfm steel tank in adelaide s.a. and what price would i be expecting to pay. I currently own a 88cfm ally and would like to trade it in if possible. it is 12 years old with a new "K" valve in test!

I'm not real sure where I'd send you in Oz for a tank beyond your local dive retailer. I'd be happy to help you out with an inexpensive tank, but then you would need to pay International Fed Ex, and your importation duties and taxes. It might still come out more inexpensive in the long run, depending on the prices of tanks in Oz.