I agree that systems sound better late at night. This may be partly explained by the different and more receptive mood that we typically have at that time. But mostly, IMO, it is due to reduced noise on the line.
Regenerators are typically a form of amplifier, so they have their own power supply, transistors, etc and behave like an amp (i.e. draw their own power, so need heat sinks). This being the high end forum, appropriate models to consider would be the Power Plants from PS Audio.
Passive conditioners types can be transformer based, capacitor based, or strange voodoo based. There is no right or wrong type. None are perfect and many do more harm than good. The only thing guaranteed, this being the high end forum, is that the best ones cost $thousands.
I prefer the passive types because they are less fuss and less likely to go wrong - but only if they also deliver the goods.
I think my cap-based Audience aR4TSS is great, but it does cost almost as much as my high end amp. And then there's the power cords to consider. and... well, I'll stop there for now :o)
I wouldn't swear to this, but I think the music still sounds better in the late hours, even with a good power conditioner in place.
My recommendation would be to get one on loan before committing.