I think it depends on the cpu,i have an 800 t-bird with an 800 core that runs 952(8X119)fsb and runs completely stable on either one of my KA7-100 boards(i have 2).Then i have a 750 t-bird with a 950 core that won't run much more then 800.
I've heard that there are timing issues with the higher core cpu's and the KX133 chipset.I think if your looking for maximum overclocking with a t-bird stay with an irongate chipset board.