Why does my system sound better??

I'll second both timrhu and zargon's hypothesis.

I have noticed osmething like this many times myself- usually when hsopping for new gear. Swappoing components in and out of the system has often made the system sound better. It has nothing to do with keeping the system on vs. shutting it off, because I do not leave the amplifier on, and don't shut the cd or pre off when swapping components. I think it has to do with cleaning off the connectors. I have noticed it more when changing electronics than speakers. Maybe this is becasue the RCAs are more sensitive / scrape themselves clean better.

Why is this getting more skepticism than cryo-treated electrical outlets?

I have noticed this also. My opinion is that the overall grounding configuration has been altered and does not return to its previous state until all components are turned off and then back on again. Try cycling everthing off and then back on and see if the difference persists.

My 2 guesses which I wouldn't value at more than 2 cents (that's adjusted for inflation too).

First, all the adrenaline that you built up and blood you got flowing from moving and positioning the speakers caused your ears to be more accurate?

Second guess, our memories play tricks on us. It's a proven fact.

Actually, a though just occurred to me; maybe the connection of your speaker cable was better the second time around. They do say to reconnect (actually clean) cables and ICs every once in awhile.

I agree with Phd,

I think the answer here might be that after components are on for a while, the circuits stabilize, they reach their optimum operating temperature & the sound will usually change for the better, could be for the worse. It may be you like the sound better before this happens!

My second best guess is the listener has not acclimated themselves to the "flaws" of the most recently attached speaker until some time passes. All speakers have a personality and none are without flaws.