You want to use 2 sticks of ram to take advantage of the fast dual channel memory mode.
You also want to pick the case and power supply separately the PSU's that come with cases are often out dated or poor quality units, for a PCIe card you need to be up here>
http://www.umart.com.au/newindex2.phtml?bid=6
For a wireless card something like this will work fine>
http://www.umart.com.au/newindex2.phtml?bid=6
What is the main purpose for the PC if it's gaming for example you would be better served using an Intel dual core or a Phenom II CPU.