Whats the temps on the 2nd rig i only see temps for the 1st rig.

now when you say the system dies? what happens? stutters? freezes? cant use it at all and a forced restart is needed?

i have a buddy running the same cards, i suggest: Core 0, Mem 400 (Samsung), sorry to say he isnt able to push his cards over that, the system just crashes.. Run these settings to get stability first then experiment.
you can also start removing cards 1 by 1 and pushing each card individually.