I use this site for comparing price on computers and gadgets between different shops. The list is quite comprehensive. The price listed on the site is sorted in price order and quite competitive. I use it mainly to check the price on computer components.
I recommend you buying from MSY and PCDIY because they are in Adelaide and you can go the the shops to pay cash. But for parts that are not available in SA, I recommend PC Case Gear and Umart.
Gaming laptops:
www.affordablelaptops .com.au
The cheapest Metabox (Clevo rebrand) barebone gaming laptop reseller in Australia. So if you are going to buy a gaming laptops, always go to this site and and look at what they have on offer.
www. logicalblueone.com.au
Another Metabox reseller. Usually more expensive than Affordable Laptops. But they have specials and is cheaper than Affordable Laptops sometimes.
Everything else:
eBay
Things that I buy from eBay include: t-shirts, posters, camcorder, watches, headphones, torches, laser, multimeter, soldering iron, can air... anything really.