I am also getting a noise around 1700-1900 RPM - only in drive and I would describe it more as a rattle, like a heat shield (but its not a heat shield)

I can replicate the rattle when in drive, whether moving, or braking in place, and reving up to 1600rpm+

I don't hear any rattle when doing the same when in Park or Neutral.

Sounds like its coming from the mid section of the car, but difficult to say exactly.

I am speculating on it being a breakdown in the Cat, but wondering if anyone would agree, and if so, how could I inspect for this before heading into the dealer? Its a 2005 with 60K miles, so still under the Cat warranty; so not sure I am upset if it turns out to be the cat.....