If you already have a GFX card is may limit your choices a little bit, since we're right at the point of another platform change... From AGP -> PCI Express.
I assume your current card is AGP, so that will rule out some of the higher end options anyway, since the 'latest and greatest' pretty much assume you have a PCI Express 16x card...
If you do have AGP: Make sure you know what type, is it AGP 1-2, or 4-8? Few of the current motherboard still support the AGP1 & 2 cards, so if you have one of those you may be looking at a different video adapter as well.
I assume your current card is AGP, so that will rule out some of the higher end options anyway, since the 'latest and greatest' pretty much assume you have a PCI Express 16x card...
If you do have AGP: Make sure you know what type, is it AGP 1-2, or 4-8? Few of the current motherboard still support the AGP1 & 2 cards, so if you have one of those you may be looking at a different video adapter as well.