umm IT IS!! lol, the X1900XTX is the best card currently out oh apart from the 7950 dual card thingy. Anyway those 7900 cards on the dell are 7900GS's (apart from bottom one) so they are not even close to as good as the X1900XTX or the 7900GT.
The x1900xtx still is better than the 7900GTX