Upgrading (at last)

[Mysteryous]

I'm soon going to upgrade my computer to something with a lot more power to it. My only worry is the choice of video card I should use. After this upgrade, my primary OS will be Ubuntu Linux. Currently I have my eyes set on a Radeon 4670 for my graphics card, but I'm still unsure on how good it will be. I plan on using this PC primarily for gaming; most notably Half-life 2 (all episodes), Guild wars (although I know it works well with wine), and other games. I just want to know if drivers are mature enough for this; and if they are, are they getting better? Otherwise I will have to go with an nVidia card, which is not what I plan to do.
I appriciate any help offered.