How to protect my amp without changing the sound?

Linear power supplies take current in narrow spikes of high
amplitude. Any impedance in the path causes proportionally
high voltage drop and the loss of dynamics. I use Furman
Elite 20PFi and cannot tell the difference. Perhaps power
factor correction that allows 55A peak current (huge
inductor and capacitor) helps. It has 4 high power outlets,
4 audio-video and 4 video optimized outlets.

http://www.furmansound.com/product.php?div=02&id=ELITE-20PFi

In addition I installed whole house surge arrester:

http://www.homedepot.com/p/Siemens-20-Amp-6-5-in-Whole-House-Surge-Protected-Circuit-Breaker-QSA2020SPDP/202562776?N=5yc1vZbm05

Audiolabyrinth, Furman doesn't change the sound or at least I cannot detect it (i don't listen very loud)/ If anything, bass got more even/musical. Strange thing is that TV plugged into video outlet got better colors, cleaner and more saturated. It is strange since display is digital but perhaps noise induced jitter on video signal adds noise.

Siemens surge arrester plugs instead of double circuit breaker. White hanging wire connects to ground bar. I cut it shorter. It protects by shorting voltage spikes to ground. Protection (most likely MOVs) are installed on secondary side of the breaker. In case of MOVs failure (usually short) breaker will trip - otherwise it provides protection for all circuits. You have to get style that fits your panel. Each whole house protector has specified max size of the breaker (always on secondary side). There are stronger protectors but require some extra space and sometimes extra panel and most likely require an electrician. Lightning is not a big problem in my area but in Sarasota where my mother lived I would install strongest panel style protection and perhaps would even double it.

No, I could not detect any difference with arrester. Furman with its tight, strong, non-sacrificial under/overvoltage protection and build in circuit breaker is probably enough but double protection sounds better. In addition I've already lost garage door opener (Chamberlain) due to the voltage spike. Chamberlain service lady explained to me, that during winter spikes are very common, recommended local Chamberlain protector and sent me brand new circuit board under warranty. This event proved that voltage spikes are common and dangerous even without thunderstorm.

Audiolabyrinth, I live in Chicago suburb. My part of the neighborhood has power lines underground. We have rarely any power disruption.

Ssglx, was it by any chance Elite DMi? (or Elite 15i)

Furman Elite 15 DMi or 15i don't have high current outputs and high current
capability of Elite PFi.