New egg apparently has the Diamond 4770 in stock. Thing is, it costs $119.99 so the only reason to get it over the 4850 is if your PSU is too weak for the 4850, but just enough for the 4770.
I realize that the mid range is where all the sales are but when you take all the stock cards they have and add all the variations created by all the manufacturers, they really don't need another card positioned in that range.