I've worked on, in, and tested Tempest/Hemp equipment.
A Tempest hardened computer used in a protected environment can survive.
Your point is valid; a military hardened computer will survive any potential electrical event but a direct nuclear strike. It will also survive a lot of physical abuse. Where can a civilian purchase one? Even if you can find one, it will cost $10k or more. Like I mentioned, Panasonic's ToughBook line is a close second...
(ps, I'm a Certified TEMPEST Professional, Level II)
