Least Expensive Power Conditioner/Surge Protector That Won't Worsen Sound

Panamax and Furman are owned by the same conglomerate now, so they share a lot of features.  I go with LiFT and SMP from either.

How dangerous undervoltage really depends on the connected equipment.  IMHO however it's more useful because an undervoltage is many times followed quickly by a power surge. Here in SC I've had undervoltage trip twice last year.  Once during a thunderstorm and another time during a wind storm. It's best to let your gear shutdown than to attempt to continue to function when these events happen.

Interesting. The Panamax models seem to have an internal device that shuts off the power when there is under- or over-voltage, distinct from the feature on higher level models that work to maintain voltage when those things occur. Of course, severe spikes will shut down the power completely. 

Unless I'm reading it incorrectly, it looks like Panamax uses sacrificial circuits whereas Furman uses non-sacrificial circuits.

"Here in SC I've had undervoltage trip twice last year.  Once during a thunderstorm and another time during a wind storm. "

You haven't seen a thunderstorm until you've seen a South Carolina thunderstorm!

No such thing for amps.  I like Tripp lite protectors and whole house for low current devices (basically everything else). 

I like this brand power line conditioner