ldimmu, I only regestered a few days ago for the same reason
I really hope the forum moderator can make a official response for nVidia about our questions. Some questions, nVidia can't answer...like the part on agpgart working, but nVidia does influence its outcome. The agpgart maintainer(s) can't do much if they don't have anything to work with.
The KT400a does appear to be better than KT400, but still doesn't compare up to the nForce2. Then again, there are rumours of a KT600. I wonder what enhancements it would have.