I don't own a dreamcast, nor have I seen bleemcast in action, but what I can say is that I think you probably might be much more satisfied using the epsxe playstation emulator with your radeon (if you have one). My recent bleem experiences on windows have been poor, and I was proud to have a few of my games running with filtered textures at 1024 resolution all in 32bit color at 60fps. Bleem hardly ever gave me such performance, and I would think that my computer is more powerful than a dreamcast.
Wait... I'm forgetting the point! I'm sorry, I can't answer your question, I don't have a dreamcast, nor have I seen bleemcast in action. {hehe}