So you want the shop to build it for you as well? Do you want to chose your own parts or just get a pre made one from a shop? What is the system for?
Your best bet on computer info in Australia for people in your situation is to have a look around Whirlpool forums as there is lots of good info there.
If you can't be bothered doing research (which you really should, it's not very hard) then no doubt the system will not be optimised for your usage and this will become more obvious in the future.
Check out this shop or this one as they seem to have the most highest feedback.