BX was one of the greatest chipsets intel made. 815 is supposed to be its sucessor, and its doing well.
BX has proven stability and suits best for workstation or server applications, especially SMP.
815 does well in high end desktop to workstation category, and is versatile with built-in display + AGP pro support.
all those Asus boards are very good and the rating would reaslly depend on your purpose, in general I would rate them in order CUSL2-C, CUBX-E, CUSL2 and CUBX.
girish
<font color=blue>die-hard fans don't have heat-sinks!</font color=blue>