AMD tends to bring out the better GPU's first. Perhaps this is deliberate (holding back the poor ones until reviews and early opinions have settled) or maybe the fab process deteriorates with age. All I know is that I have always had better clockers when purchased near launch than near end of production. This applied for 7xxx series when most reference launch cards could hit ~1200MHz, but few newer cards appear to do so now. The 6xxx series also seemed to clock better on launch/reference cards.
My opinion is that non-reference cards are made to save money or to up-sell a product, rather than increase real performance. A better cooler may well increase performance (especially on a card that throttles when hot), but PCB component changes make little difference. For a while I had the world's fastest air-cooled 7850. It was a reference VTX card which benched 1400MHz and was stable at 1350MHz once I fitted an Accelero to keep things cool. The GPU is key, and that is a lottery which no pcb changes can circumnavigate. Go for the cheapest one you can find with the bundled accessories/games you like. If you really want a quiet card wait for non-coolers, but if you really want to overclock it may be best to buy now and fit your own cooler later.