Sometimes my system sounds great, sometimes awful

In addition to the incoming power do you have a dedicated circuit for your system? Not sure if that would help but when I added 2 for my system the noise floor dropped significantly. That being said my incoming voltage varies from 119V to 127V and I hear no differences at either extreme. Before I knew my voltage was all over the place I added a 2.4KVA balanced isolation transformer that lowered the noise floor even more. Since then I have taken it out because there was a 2V gain on the output and at 127v I had 129V out. Can't be good for my tubes. Personally when funds permit I'm going to look into voltage regulators.

"Do we hear differently depending the time of day, our mood, heat, cold... other circumstances?"

You left out recent noise exposure, current condition of sinus's, current emotional bias (I just changed this thing so now I'm going to believe music sounds better or worse), social pressure, humidity, ego, and probably lots of other stuff I'm not considering.

On the bright side, your knowing about all this stuff ("tell myself to wait until the next day") can save you a boatload of cash over the long haul and keep you from stepping backwards now and then.

Power problems certain time of the day dude.

>>Sometimes my system sounds great, sometimes awful<<

Don't listen when it sounds awful.

Read a book or play Angry Birds or get drunk.

Maybe a nooner with the wife.

IMO
YMMV

It seems that many of you agree that power conditioning is a good thing. What is a reasonable power conditioner solution that doesn't break the bank?