Taxes only apply to orders over a certain amount??

[DrByte]

Is it possible to add 10% GST for orders over a certain amount only, e.g. $1500?
e.g. most transactions would not have tax as most products on our site are under this value, but taxes do apply on some wholesale orders so can we set the cart to add the tax at checkout (to the total amount, including the shipping of course)??

There is no built-in ability to calculate tax only on orders over a certain amount. Although, custom coding could be written to handle that on a case-by-case basis.

Also can I have certain products marked as TAXABLE (e.g. in my case a few very expensive products like those that are over $1500 each etc) and those ones show both an Ex-Tax Price (in red, for USA/UK customers) and an Inc 10% GST Price (green) for my AUST customers that I have to charge the tax too?

In terms of marking certain products taxable or not, esp based on what zone a customer is in, you can do that simply by setting up an appropriate tax class (perhaps called NonTaxable) and link it to the zone where no charge is applicable, and give it a rate of 0. And then use the default TaxableGoods class, tied to a taxable zone and appropriate tax rate, to handle those who "should" be taxed.