I run a Australian based business with servers based in Australia in our data center but i would like to target the U.S market as well to try and get more business
If you're looking for something strictly to serve U.S. customers, and it doesn't need to interface with gear back in Australia, I'd recommend you stay U.S. Central. Your main contenders will be Dallas and Chicago, of which I would recommend Chicago for the additional opportunity of serving Canadian customers will reduced latency.
If you decide to go with Chicago, try GigeNET. They should be able to accommodate your needs, as they have done so for me numerous times.