Actually, looking at the information it pretty much looks to me like it will work *without accelleration* if you don't try to force the driver software to work. (ClassicHasClass says it will work unaccellerated in a Quadra. As does another page on LEM.)
The benchmarking says the card is less than twice as fast with the accelleration enabled vs. disabled, so it's not as if the card is light-years faster with it enabled. (The Quadra's built-in video is faster than *most* compatible video cards because even though it's just a simple framebuffer it's on a considerably faster bus than NuBus.) So if the reason for installing the card is to just get more screen real estate for palettes/menus/whatever it should work fine. Just play your video games on the built-in video.
I sort of doubt there's any risk in just plugging the sucker in and trying it, as long as you're sure the card doesn't have any electrical problems.