Looking for an upgrade path that will suit both your existing AGP board and a future PCI-Ex board? Some very nifty things have come out of Hightech Information Systems recently that can do just that. Recently they have been demoing hardware at this year's Computex, including three new video cards, one of which will be able to switch between AGP and PCI-Ex standards. The HIS X1600 Pro Dual DVI "Dual Interface" card has connectors on either side of the card and opposing DVI interfaces that, with the flick of a switch, result in the card being able to toggle between AGP and PCI-Ex functionality mode.
They are also releasing a card aimed at home theater, which will be a base X1600 that has a low form factor (though it makes up for this by consuming 2 expansion slots), HDMI and Dual DVI outputs and more. They're also creating an offering for the low-cost market in the form of a PCI 1x X1300 card. Interesting stuff coming from HIS, they may be worth a second look.