Hi JJJ,
May need to stretch the dark frames to 50 or 30 in photoshop or the likes to really show the difference.
There is also some info here:
http://www.astrophotography.id.au/new-camera-purchase/
And here:
http://www.centralds.net/cam/?p=1687
P.S. still waiting for my CDs-600d but not long now
Cheers
Anthony