Not sure if you can trust the seconds store you're shopping at? Thankfully, two vendors in Australia sell their refurbished wares directly to the public.
Sure, you could sign up to Catchoftheday and wait for whenever the latest excess stock from Asus, Samsung, HP or Lenovo turns up, or even peruse the likes of Grays Online, looking for cheaper equipment. But if you want immediate access to refurbished stock, both Apple and Dell have direct sites available.
You'll find that current- and last-generation products are available, usually for a decent discount. Most things on Apple's site are covered by its limited one-year warranty, while Dell's warranty will vary depending on the product. Both companies will allow extended warranties to be purchased, with Dell's monitors being the exception and limited to only one year.