Afaik, all the AMD partners are bringing out non-reference designs that look to have a better cooler, but often have less coper in them,aswell as cheaper ram/volt chips, which reduce overclocking or completely disable it, to increase margins/reduce production costs.
Had to swap my PCS+ (not a bad card)for a HIS refence board for a ek block to fit, and it seems no-one has any reference 5850s for sale anymore. I belive the 5870s are still reference, but as most people here and other forums know of how fantastic the ref 5850s are (5870 o/clocks+), they seem to have all gone.
If not going for watercooling, i would have a look at the PCS+ / Vapour-x/Toxic, cards for both 5850/5870
Edit: Not sure about Asus, but they may still be reference as their advertised as 'voltage tweak'.
Allso, if you do want to send it back, do so asap as the 7 day Distance Selling Regulations applies afaik.
Hope that helps :]