Matrox have too much of a bee in their bonnet about image quality preservation*, it's the main reason why the Parhelia series really suck for 3D performance.
The amount of image compression that goes on with most 3D graphics cards when drawing 3D is unbelievable, and the Parhelia is trying to keep up when the amount of bandwidth required to push through uncompressed 3D textuers is huge.
* - When in 2D, you're only drawing a single 'picture' at whatever resolution, the memory usage and bandwidth required to do it at a reasonable rate has been available for a long time now. When in 3D, each different wall/floor texture is an image in itself. A good comparison is this - just imagine if, when you browse the web, all images on web pages were uncompressed bitmaps, and you're on a modem connection. You'd have to wait from here till next year for each page to load :-). With some decent image compression routines, you can make the images look near identical to the original to anyone looking at the image and not zooming in on it.
Heh - that's impressive - all the images on that Matrox site URL are broken :-)