Just wait for the patches to roll in. Carmack has been ranting about fake OpenGL functionality in drivers for ages and since OpenGL is so underapreciated in games, this shit just happens. It will get fixed in two months. And if your computer can't handle the texture speed with 64bit Windows (or compatible) adn texture cache on large, than your computer is seriously outdated.
If you can't play Rage because you can't handle the visual information than you need to get your brain checked (I mean, how do you cope with real life, or are you so autistic that you need to rest every two hours or so in a small room?). It's not id's fault people suck at thinking and gaming.