Sigma DP1: wide & slow, too much dough
28mm, f/4, maxing out at ISO 800?
This is mostly an outdoor camera, since you'd be hard pressed to shoot many interiors, especially without image stabilization (IS).
BTW, the G9 sensor measures 7.6 x 5.7 mm, and the DP1 is 20.7 x 13.8 mm, so that's 6x the area of the G9. I don't think you can get a good image at ISO 800 with the G9, but then again it has IS.
If it were 35 mm, f/2 with close focusing, and an acceptable IQ at ISO 1600, it might be doable for <$800.
It will go for $999.