Build a Listening Room within the Basement,
say13 wide x 20 deep, x your height (NOT a square) Then your materials/surfaces/reflections will be much easier to deal with.
Others can suggest ’better’ room sizes, and then, within that space, try the speakers on the short end, or along the longer side walls
I have always had my speakers on the short ’front’ end, i.e. currently
https://www.audiogon.com/systems/9511
btw, my speakers are on wheels, easily adjusted toe-in for one listener or two (both off-center), and: for best listening, I roll them forward and in, further away from rear and side walls.