[Gama]

When you stack images, you dont really go deeper very much in Magnitude as youre exposure is the initial period in this case 3 minutes, so stacking will just sharpen and remove noise to the image and bring detail out better. A proper 9 minute exposure will go very deep in magnitude, and go much fainter than a stacked equivalent. But when you live in a suburb with bad light pollution, you arent going to see those specs of faintees of stars..
The good thing about the 300D is its got a better Hot Filter than the D200 in terms Astro work, but i agree the Canon's are are good Astro camera (I own a 20D), i just think that the Nikon CCD sensors are better.
With the image you took, it was taken with a 150mm (6 Inch) lens, not a cheap 60mm (2 inch) telephoto, so you cant really compare timing exposures.
Remember your aperature determines your depth of magnitude, so 60mm isnt going to give you much.
But your missing the point of the whole test, that is the noise. As i already know the CCD sensor is better, it was the noise that had me worried. Well, even with the harsh filter and small exposures, the quality texture and smoothness of the images just verify that it does well. Your image was at 400 ISO, mine at 800 ISO so mine should show more noise in the image, yet your image shows a higher level of noise as you said.
I took a 2 minute exposure of M8 thru my 14" RCX @f5 heres a crop of the centre as i had severe vignetting, again, its smooth and not grainy like most CCD cameras, even my SXV-H9 is not as good in terms of grain and texture.
There is NO enhancement, and the full version had no noticable amp glow either so the threshold for it to be visible is around 18 deg +/- 2 deg (RCX has an ambient temp sensor). Sorry about the tracking errors.
More to come soon if weather holds.