First, you shouldn't compare the X1900XT to a 7900GT, the X1900 kills the 7900GT. If you're going to compare a X1900XT or an nVidia card, compare it to the 7900GTX.
No, im going to buy a 512Mb version 7900 GT and overclock it to a GTX level, thus saving millions. Course the 512Mb version is the same price as the X1900XT and it dosent need overclocking to be an XTX (i dont call 25Mhz overclocking). But then the GTX has 1.5x the texture fill and the XTX has 2x the shader power, but the shader power is overkill. Woh, what were we talking abt again? Oh, right.. PureVideo isnt as good as AVIVO, how come? and how come some Nvidia cards have AVIVO?