Power conditioners

All of today's technology for EMI and Surge suppression has been around since the late 1970's.  What's improved since then is a reduction in size, cost, and a potential increase in power handling capacity.  Just like any other analog circuit design, the topology is as much art and philosophy of the designer as it is a science.  There are many ways to achieve a given result, and some are much better than others. I'm not saying one brand is better or worse than another, but I am saying there are differences between brands and the retail price doesn't guarantee a better product. This is especially true of companies who don't publish attenuation curves or power handling capacities.   In this case it's buyer beware, you just don't know for sure what you're getting.

BTW, do note that some sacrifical circuits, that is they self destruct in the case of a surge beyond their design limits, shorts the input to your equipment.  This causes the distribution panel circuit breaker to trip and input fuse to open, so your eqiupment is put in a safe state.  That's hard to beat. 

True story - years ago I was designing such a circuit for green energy company, so I decided to test it. I removed one back to back diode, so it would trip on the negative going voltage of the AC Mains. I wanted to see if the circuit would protect the downstream op amps and circuitry. That one 1.5 KW diode with nanoseconds response time blew but before it self destructed, it blew the 200 Amp breaker on our distribution panel and also blew the AC Mains breaker on the 3 phase input panel that powered our half of the industrial park.  That caused a sudden huge surge imbalance in the other two phases, which triped those breakers as well.  There were a lot of unhappy prople in the park, but our circuits were protected.  Bottom line is a well designed protection circuit will protect your expensive gear. 

@tcatman 

Panamax and Furman are now owned by the same parent company.  As such, some of the Panamax and Furman units offer Series Mode protection.  While There are MOV’s in them, they are not MOV centric.  That is, the MOV is there to cover a rare edge case.  

My suggestion is, as always, use a whole-house surge protector in your electrical panel.  These are almost always MOV based, but are in the perfect place for MOV’s and usually have some device to tell you when they have been used up. 

Then use Furman with SMP (or whatever equivalent series mode protection you want) near your audio gear.  Related to your next question, because SMP is essentially a low-pass filter, they tend to work much better than a lot of EMI/RFI filters.  They start filtering noise around 3 kHz, which is actually super low compared to a lot of EMI/RFI filters which claim to start filtering around 50k-100kHz.  That is, SMP filters AC noise all the way down to the audio spectrum.  

When shopping for a Furman, make sure it says "SMP" to ensure you buy one with the series protection features.  They make many models which do not have series mode protection.  

“Everything we hear can be measured” is an unsupported belief.

@kennyc + 1

@larsman It is true there is no one measurement that correlates to what we hear.  The THD Wars back in the 1970's didn't help anything either.  But the fact is, the vast majority of ugly distortion mechanisms can be measured, if the engineer is creative and has the right equipment.