I live in a rural area, prone to power outages and voltage sags during the summer when everyone (including us) have the a/c going. My "A" system has evolved since I became enamored with audiophilia (is that a word?) and my system's components are very revealing, about Everything. After investing significant $ in high quality speakers, tt, phono preamp, mid priced cd player and even an Otari 1/2 reel to reel (recently) and an 8 ft bass trap in the one corner, the sound was the best I've ever heard, with one exception... there was something else going on that wasn't on the media I was playing. Everything pointed to my power... which was standard house wiring fed by a main circuit panel two stories below in the basement at the opposite end of the house.
I did due diligence in my research, and decided it had to be the power. Timing was perfect as Music Direct had the PS Audio PerfectWave P3 Power Plant on sale for $1k off. SOLD! Well the difference was breathtaking. The music now appeared out of a black background. What noise floor?? I am convinced, if you have house wiring and dirty power, the puny filters in most audio components just can't clean up the mess. Granted, $2.5k+ for a good quality condition (even $1.5k on sale) to clean electricity I was already paying for is a bitter pill to swallow, but I'm glad I did. Of course YMMV, but in my case, it was $ well spent.
btw: I have a "B" system with lesser, but still quality components. A ss amp with phono input, a $2k tt, and vintage but in perfect condition Klipsch speakers, and there is a noticable noise floor when I turn up the volume of the amp. Not just a 60hz hum (albeit very low level) but other stuff I can't really describe. There is no doubt in my mind that this noise floor is "coloring" the music in some way. I can live with it as my "B" system is used for casual listening. Doesn't happen with the "A" system. A proof in the pudding if you will, that the P3 is doing it's job.
Good luck with your research.