I would also go w/ the MSI nForce2 mobo. Been a loyal MSI user for the past 3 years, Asus before that, and have used 4 mobos from KT266 rev. 2, KT266A, and two KT400. From what I gathered, MSI makes the most stable mobos, has its fair share of tweaks for overclockers and non-OCers alike, and the price is more affordable compare to OCer mobos by Epox and Abit, or over the top mobos like Asus.
I'm planning on buying either the MSI MP K7D Master or a K7N2 nForce2 mobo.
From preliminary reviews, the KT400A chipset still lags behind nForce2 chipset in speed.
My final choice would be the MSI K7N2 Delta.