In games?
The KM400 is a more a movie and dvd video card, has a built in mpeg decoder. Gaming should be OK with fast ram (PC3200 or PC2700) but it will not play games as well as a nForce2 IGP with dual CH memory.
I built a system with a Biostar M7VIZ , best KM400 board IMO, and it was fast and very stable. The 2D was great and the few games I played with it did fine. Mind you I did not put Unreal2004 on it etc...