When I did a listing yesterday mourning according to lowest price, the Diamond came up the cheapest (with the extra 5% discount and rebate + free shipping)
They may have put the Power color on sale afterwards, the Diamond is still a bit cheaper ($426.49) vs ($429.99) though a bit more trouble with the rebate.
I had always thought Diamond was a good card (though I admit it has been a long time since I owned one) and power color was one of the "cheaper" brands.
Anyway, I will be more careful in the future about posting deals in these forums
Diamond isn't great on quality control. I'd rather spend the extra 30$, incase I need the customer support, and for a generally better quality card.