Lotto wrote:GeForce FX cards and up support all the features in DX 9.
Radeon 9500 and up support all the features of DX 9.
What this means is in games like Halo, you get to see all the graphical details the developer intended you to see. If you have another card, you will still see good stuff, just not everything the developer intended you to see.
Technically, DX9 has alot of features that developers are using to make the game looks better graphically. such as shades, shadows and that kind of stuff.
Cards from FX5200 up, and Radeon 9500non-pro up, support DX9 like you said, so that's why the DX9 is so important to the gamers.
Graphics are built on many of the features DX9 has to offer, and if you want to enjoy them, you need the right card for it.