You really do need a tower case.
I suppose you could get one of those external big PSUs that were popular for a while years ago (but very rare now)...but...
It's not just power, it's heat. A standard desktop just doesn't dissipate the heat well enough, and the PPC card will get crashy and might even eventually burn out. And then there's the space problem of adding a BVision gfx card later...
