Gama,
Thats interesting about ISO800 and lower being devoid of the median filter (well its some sort of filter). A very interesting development and to me would remove the biggest negative of this camera.
From what I have seen IO400/800 is about optimal unless you do very short exposures.
I agree QE increases dramatically with the removal of the hotfilter, but primarily > 550 nm. Around green it makes a few percent difference.
So you have a hard time understanding French? This is where I got my original information to modify the 300D
http://www.seo-e.co.jp/hobby/EOS300D/EOS300D.htm
Terry