Components for RT.X100 Xtreme system

My boss has appointed me to build him a custom video editing computer
built around the RT.X 100. The basic design philosophy is to build the
best possible system, regardless of cost.

This will be his second system build around Matrox video hardware; the
first one was done with a Tyan Thunder K7 dual-processor mlb and an
RT2500. It was a royal pain to get working, and I would like to avoid
that this time.

So, I would love to hear from you folks who have already done this.
What did you put in the box along with the RT.X100?

What motherboards did you use? how would the fastest single-processor
Pentium-4 system compare with dual Xeons? With dual Athlon MP?

Has anybody used ultra-320 SCSI drives?