Brick Wall offers a couple of power conditioners/protection. I can’t say about the improvement in sound, because I am just using one for my computer.
To my liking are the old BPT power isolation transformers, which were rated high over the need for current in many systems. The one that I bought many years ago had 6 secondary windings electrostatic shields for each winding, and also produced balanced power in the output. Each secondary is rated at 10 amps, but the primary is also rated for 10 amps, so that must be taken into consideration.
Got to admit to using Richard Gray products in the past but think that more than one needs to be considered.
A close second in my experience is an old PS Audio P300. I have one coming in Wednesday that has been thoroughly rebuilt by a good friend of mine who used to consult for Sudgen in Europe. I consider the extra money spent on the rebuild rather worth it. I have owned these units (the P300 in particular) like what they do given their limitations. Almost always used for source equipment.