I'm having a really hard time with: "Power cable reduced my soundstage"...

Power cables have zero influence on sound stage.

Power cables can inductively couple with other cables. This will cause noise from other cables EMI fields to be transferred to the power cable in question. Similarly, when inductive coupling takes place, the EMI field of the power cable in question is transferred to other cables. 

Much of this inductive coupling can be mitigated by isolating (not bundling) power cables from other (power and signal carrying) cables.

When isolation is difficult or impossible, the use of ferrite beads can isolate the noise source. This is why switch mode power supplies have ferrite beads on their input and output cables. 

Shielding, when done properly, can be effective. I say “properly” because most unbalanced audio cables use the shield as a signal-bearing conductor. This causes induced noise to be brought directly into the signal path. The correct way to shield an unbalanced audio cable is to add an additional layer of shielding which is isolated from the signal-bearing conductors, and tied to chassis ground at only one end (preferably the source side). Typically the most convenient place to ground the shield in audio systems is to the preamplifier chassis, as the preamplifier is the hub of the system. 

Going back to the OP’s claim about loss of sound stage, that is due to other factors. Most likely speaker placement and phasing. 

EMP pulses from lightning are almost always induced on to utility (any kind - power, telecommunications, etc...) wiring that runs through areas where lightning occurs. It is the combination of very high levels of magnetic flux and the great length of cable that is exposed that results in the massive energy transfer. The only way to mitigate resultant surges is to use a secondary surge suppressor at the main electrical panel board and surge suppression at the equipment that we want to protect. These usually consist of voltage clamps that permit relatively safe levels (up to about 200 volts rms) to exist on the circuit. Most often these are MOVs, but can also include high current zener diode arrays and gas discharge tubes. It’s important to know that these devices are all sacrificial in nature, and need to be checked for functionality on a regular basis. It’s also important to have your home electrical system inspected for damage whenever a major surge is experienced, as extremely large amounts of energy can be dissipated in wiring, receptacles, circuit breakers, etc in the event of a major surge, causing permanent damage and potentially rendering the electrical system a fire hazard. The best measure of protecting our valued equipment is disconnecting from all sources of surge ingress in advance of lightning storms. 

A shielded power cord would have zero effect on taming a lightning surge. Truthfully, the lightning surge was mitigated by the sacrificial action of MOVs in the power conditioner. The damage that took out the Krell and its power cord also damaged house wiring and related components (panel, sub panel, receptacles, wiring, etc, etc,) and that means rip and replace all of that too. You should hire the services of a reputable certified electrical contractor to assess the damage to your home’s electrical system, and get in touch with your homeowners insurance provider ASAP.