Erik -
If the spike your equipment encounters is coming from the same branch circuit feeding it (say a wonky vacuum cleaner in the next room), the spike will probably get to your components before it is snubbed by the WHSP back at the service entrance panel. It can be tough to explain that to the cleaning service. BTW, my WHSP was a Square-D that I installed when putting an addition on my house back in 1997. A big, clunky 7" cube I mounted next to the SE panel, but I never lost equipment to a surge, and that is a lot of service years.
On the topic of MOV's - they absorb surges until they can't, then they pop. If the surge is a long one or a big one, there may be enough of it left to still do some damage beyond where the MOV USED TO BE, and if it is a tree branch shorting between phases or worse - to a higher voltage circuit, the MOV may now be just a couple of leads with an air-gap between them.
The VR feature you mention can be quite valuable, although it may not be a big deal with all solid state equipment because SS runs at low voltages internally, and a swing of 20-30V on the line may end up being quite low once it gets past the step-down circuitry in the device. Even so, the dielectric stress, across the tiny dimensions within the semiconductor chips can still be impressive. OTOH, with tube equipment, especially older units that lack VR in the device, when the line voltage is stepped up for the tubes themselves, that swing is magnified and is more likely to impact the sonics and life of the tube. When the unit was designed and tubes cost $5 from your corner TV shop, that was not the concern it can be today. Probably most people have had a "brown-out" at one time or another caused by a tree branch shorting a power line to ground in a storm. Worse is when a higher voltage distribution line gets in contact with the low voltage feed to your home and raises the voltage to your place by a couple orders of magnitude. I had that happen to a customer and the utility company got to replace a bunch of stuff for them. Hardware can be replaced, but not so easy to rebuild what is on your media server.
It is an uncommon step to take, but having a device (or simply a single connection to unplug and air-gap your sensitive stuff from the outside world) can go a long way to protecting you. Keep in mind that you should also disconnect the cable feed to your cable modem and protect the power feed to EVERY point on your network. A surge or non-standard voltage can come in through ANY point that is not protected and will continue until it is snubbed or it literally burns out the circuitry -- be it a semiconductor, capacitor, or even a trace on a circuit board - an effect that is usually terminal for the device. Unfortunately, a good spike can often turn the diodes in your power supply rectifier bridge into fuses, and they seldom just clip in.
