seemingly resolved of the most recalcetrant xw8600
Replaced the power cord with a 14AWG cord vs teh 18AWG cord, this did not resolve the problem, but did show there werer two failure modes. One mode was power on, no post, the newly observed failure mode was that the system appeared sequenced and appeared frozen, but in actuality was the lack of video on both of the two displays.
We swapped the video card with another xw8600 and observed the problem follwed the card. Several days of operation verified the first machine remains stable. We will now obtain a couple replacement video cards and expect all to be well.
Much appreaciated are a couple messages of advice!
Bruce