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

Don't know what your price range is, but I use a SurgeX sa-1810 and hear no sound degradation.  Been through many lightning storms here in FL and no damage to any components.  It isn't as pretty as the others, but it's  A-1-1 Certified - the U.S. Government's highest classification for surge protection.  No sacrificial MOV circuitry.

Here, 'A' means the product suppressed 1000 worst-case surges (6kV at up to 3kA) without performance degradation, the first '1' corresponds to the 330V protection rating class, and the second '1' means no ground contamination – no surge current dumped to ground.

Put together, A-1-1 represents the best power line surge protection certifiable under ANSI/UL 1449-rev3.

The rating that counts with SurgeX surge protectors is the one thousand 6000v surges it withstands to be "A" rated. Unlike standard surge protectors SurgeX surge protectors don't wear out due to repeated surges. 

I've had good luck with Audioquest Niagara.  Tried many over the years (a few mentioned above . . . ) and my latest move further into a rural area has me contending with power issues 'big time'.  This unit has successfully handled them 'and' its one of very few units that doesn't affect the sound.  Had some pretty pricey products mentioned above not cut it in that sound department.

Ah yes, as erik mentions above . . . I still rigidly decouple the entire deal from energized during lightning storms.  But my power issues were interstingly enough not to do with electrical storms so much as reductions in power followed by surges.  That Audioquest seems to handle them in that no damage.  That didn't happen when I first moved into this place with no protection and I had a $$ Plinius repair bill to deal with.

+1 on Chang Lightspeed

Brick wall out of PA for $300, matched several-line conditioners in the $1500 

range andSterphile used to have it in class-B  which is respectable ,I bought 2 and find them pretty effective ,I upgraded mine by upgrading  several internal capacitors 

and installed a Furutech power cord to make it better still , most everything can be bettered if you look inside it ,whst most Audiophiles don’t realize is Thst on average 25% of the-cost goes into the build ,the rest R&D  overhead,and dealer mark up.