For that kind of money I would buy a used 6970/50.  You can find them around 100 bucks and get 470khs out of them pretty easy.

If warranty is what you are worried about XFX is lifetime, but they are known for using cheaper components(not necessarily that they fail easily but they don't overclock as well)

Also, takes me back.  Ever played duck tales?  I remember our second computer was so fast (cyrix 100mhz cpu) that you couldn't see the hook spinning on the rope.