This is actually a complex subject. You could read the Master Handbook of Acoustics and use the required room optimizer software and then hope you get it right or you could hire Richard Rives who is an experienced acoustic engineer specializing in home audio. When and if I build a new home, that is what I will do. Your room has a lot to do with the quality of the sound. My recollection of the handbook is that it gave a range of desirable ratios and suggested a minimum volume.