for some ideas in aus i recommend msy.com.au and pccasegear.com for parts shipping was reasonable and if you live locally to an msy you can save a bundle by going into the store...
your budget seems pretty good, you could literally almost get all of the best gear going round for that kind of money, even in high price AUS
edit - for keyboard/mouse do you have a budget in mind for those, as you can go cheaper on those items to save for more cash elsewhere