I tried all the brands at harvey norman and narrowed my selection to tempur, serta (mid range highest spec), king koil residency. King koil residency because my wife used to have one previously.

In the end I opted for the king koil residency as it is less than half the price of the tempur and serta while still providing the necessary comfort and support. I recommend you check it out. If price is not a factor then serta would have been the winner.