I want to clarify on recommended video cards.
The features used most definitely don't require full DirectX 8.1 support. Not even DirectX 7. Theoretically, actually, everything *should* work on a TNT 2, just slowly.
As for recommended cards, if you're going for cheap, get a Radeon 9000, 9100 or 9200, in any of their flavors (They should be ~50$ - www.pricewatch.com
). They are vastly superior to cards like the Radeon 7800, and should be in the same price-range. If you prefer nVidia, go for a GeForce4 MX which are dirt cheap, fairly fast, but have bad feature support (no Pixel shaders or Vertex Shaders, unlike the 9xxx Radeons). Or, you could go for a GeForce4 Ti4200, which should be under 100$ as well.
If you're going mid-range, I would most definitely recommend the Radeon 9600, which offers DX9.0 support, and is vastly superior to the competition (GeForce FX 5600), and better priced.
High-end is, as Bobbau said, Radeon 9800, in any flavor. The cheapest are around 300$ at pricewatch.