I have a question, were can you actually find if the card is reference or not? I have two GTX 470, that I got for gaming, and I've only ran across a random forum post saying that they are reference PCBs even though they have non reference coolers and clocks to then.
Reference cards aren't made anymore, and they specifically don't have custom coolers etc. on them. If you see a card with a special cooler or similar modification, it isn't reference. If you want to be absolutely sure if it's reference, look at the card itself and to the left end of the PCI port is a small black two-point horizontal switch. If the switch is there, it's reference. If not, it isn't.