whole house surge protector

I installed in Siemens electrical panel two Siemens 60kA BoltShield protectors.  They are in the form of dual circuit breaker and just plug-in into empty spaces in the panel.   You can as well install Siemens FS140 that will work with any panel.  Yes, most of MOV based protectors clamp at 400V or higher, but voltage spike produced by lightning or broken power lines (like during icestorm) is very short, reduced further by filtering effects of wire inductance, limited transformer frequency response etc.  This is first necessary step.   In addidion my system is plugged into Furman Elite 20PFI power conditioner with tight non-sacrificial over/undervoltage protection.  Still, during thundersorms, or when away, I unplug.

As for negative effects - Parallel protection like MOV based surge protectors have none, while my Furman has high current outputs for the power amp.  I believe there was slight difference with my previous amp but none with the current Benchmark AHB2.  It is likely because AHB2 has line/load regulated SMPS.

Absolutely a good investment.  No question.

For years I have had an Environmental Potentials 2050 installed on my panel. Said to reduce any noise in the line and provide surge protection. Glad to hear about these other options.

Do it. I did it back in the 1990's plus an additional independent panel ground.

+1 EP 2050 & 2750.