I think with the current XDarwin packages, there is no way to accelerate the video. I'm going through the same thing, too. The slower your CPU, the slower the XDarwin display. I mean, there isn't even an XF86Config file. I don't expect acceleration when I"m running it through quartz, but when I log in at the console, I expect speed close to what YellowDogLinux was giving me (blazing).
I'm guessing, and remember, this is a guess, that if you download XF86 from xfree86.org (they have darwin/ppc packages), that you would get the full-blown X distro, with accelerated video, but I could be very wrong about this.
Hey, does anyone know when we will see Blender for Mac OS X, and if it will run in aqua or in XF86? Just wondering (waiting). The website says Q3 2001, and I don't know when the 3rd quarter starts.