Adam2,

With common solar storm activity, I would tend to agree with your conclusion. If however we are considering a large magnitude X class flare, then all bets are off on amplitude. However, such events are very rare, and have other far more immediate consequences. My point is that the sun is capable of producing solar activity sufficiently strong to match the signal amplitudes found in EMPs

It's been my experience that metal cased equipment, whether referring to the chassis alone or placing the equipment in another metal container, provides only limited protection. If the metal case is grounded, the protection is improved, and could be enough to negate lower EMP amplitudes. It is scalarly proportional, and some protection is always better than none. My contention is that by the nature of the threat, at or near the very worst EMP event is a likely outcome should the threat manifest.