Centre Com

I buy a lot of stuff from Centre Com and have never been disappointed. The Clayton store is the Bunnings Warehouse of computers — it is huge. If they don’t have something in stock, it probably hasn’t been invented yet.
While their website is extensive, if often pays to check in-​store as they often have one-​off specials and great bargains.
I just had a custom computer built for me. The sales person took me through all of the options and gave great advice, then called several times as the build progressed. Very happy with the finished product.
My only criticism would be that, like a lot of businesses these days, they are applying a surcharge to credit card purchases. They do explain this (repeatedly) so it is your choice to either pay this or organize another payment method.