Isn't Grim Fandango DX7 ? Anyways... XanderF word of advice. Since you aren't sure if certain games you own will work on either of the cards you are suggested I would suggest you go to a brick and morter shop like Best Buy or better yet Circuit City (If you have one of these). CC has the best return policy out there and buy the card there. This way you can bring the card home test it out on your machine and if it doesn't do what you want just bring it back and exchange it for another card.
You'll spend more money but in the end you'll have a card that plays the games you are playing.
Grim Fandango is 3D rendered. What type of 3D is another story. Even some Neo-Geo games render 3D backgrounds while the Characters are 2D. A game can render 3D via software or hardware, but it might be rendering the 3D models differently then how you see it in todays games.
D. Solomon Jr.