I would like to improve the sound quality a bit, because the upper mids appear a bit too pronounced and I could use more specific placement of instruments in the audio spectrum, IMO.I think you should start with some room treatments on the walls to absorb standing waves. This is the first step in trying to tame upper mids and highs. Think about it, bare walls create a perfect surface for upper frequency sound waves to bounce around the room.
Try the "clap test"...clap your hands and listen for any echo in the room.
For better imaging of instruments, first try pulling your speakers forward, away from the front wall. Also try varying degrees of toe-in.
That’s a good sized room, maybe move the speakers farther apart.