I too am using a Powershot (A630 to be exact). I guess I will play with the lighting somemore. My issue is that while my shots seem to be OK, I always seem to be able to see the crystal. For instance (see below collage of your's and mine).
Look at mine. You can see that the crystal has sort of a haze on it (reflection), while on your pic you can't see the crystal at all! Thats the shot that I am looking for, where it looks like there is not even a crystal present. I'll try some different angles or maybe try to difuss the light a bit better. Thanks!