What power conditioner will help in my situation?

Clean up the line AT the ceiling fan.
If you can get at the wiring above the fan add some ferrite claps on each of the wires.
Two on each would be good.
Then at the wall switch, in the wall, add more.
This will really cut on the electrical feedback.
So you will have less to worry about at the wall socket for your equipment.
I have done this to my refrigerator.

The sort of ferrite which clip on would be easy. i used 1" barrel ferrites placed on the wires and wrapped the frig cord around another.
Also there are small in wall conditioners which fit in a standard AC duplex spot. Maybe you could add one of those to the FAN. And kill the fan problem in the fan part of the circuit. Either in the cieling or at the fan switch.

Just shut off the fan when listening to your stereo!

I turn off the AC or heat, due to fan noise and circulating air, when I listen.

"I turn off the AC or heat, due to fan noise and circulating air, when I listen."

I guess many of us do. I do, but there is that other problem, "Is your refrigerator running?" which despite the old joke many of us do wish it would runaway considering the disturbing noise these modern refrigerators make. Smaller homes where listening spaces are in close proximity to kitchen is real concern, for unlike AC/heat shut off at thermostat, shutting off a refrigerator full of food invites real risks.

Aperez -

a dedicated line to your system would be the best option.

I had that same problem before I put in a dedicated line. The switch for the ceiling fan was one that allowed you to increase or decrease the fan speed. I changed the switch to a simple on/off switch and the hum disappeared.