Ceiling fans, bad news they blow the sound stage image around
I have a similar basement set up, with central air in the rest of the house. I find that if I keep the basement door open (just a bit) when I'm not using it, the cool, dry air eventually works its way to the basement. I rarely see more than 70F down there, but if it becomes a little uncomfortable, a small fan in the corner of the room provides just enough air flow. I can barely hear it from my listening position and I find it is not a bother when listening to music.