Originally Posted by
Benfinkel
So,
X700 > X1550 while X8600 < X8800. Core clock speeds don't matter, neither do amounts of RAM, ram bus speed or pixel pipes except of course when they do matter. A DX transition does matter, but the age of the engine of the game does not, in this case, come into play. There are some "series" changes in there, but you wouldn't know from the manufacturer, just from one online retailer.
On what criteria, besides running the game in question with various cards, can you make an educated guess at how well a card will run it?