firstly, yes those brands are good and dependable, asus has proven itself to be a good mobo designer
, western digital is probably the best in its line in making hard disk drives and for rams either kingston or corsair would be a good bet.
prescott is the newest processor on the block, and it is by intel, the only con of this processor is the high temperature output which 75C is normal, whereas for other cpu, 50 is the norm ><, thats why u need a number of fans or better still a water cooler... hmm
the ati radeon 9600pro is a nice graphics card and it is not entirely outdated. If i were u I would choose the 9600 series over the newer 9800 series, this is because the 9800 series tend to need more power and it is so much more expensive... dang, though of course the 9800 is more powerful than the 9600.
The 9800 series is just a tad improvement of the 9700 series and they cost around AUD600 each, not a good idea, just stick to the 9600 ok?
About goin to the local stores, I dont know much about that but it is better to go to an area which has alot of computer stores which are not branches such as harvey norman. This is because they tend to do alot of competition which is good