Among many many parameters, I'd say the single most important one is the speaker itself. I own several, and I find that usually, bookshelves sound the best at low volumes. If your room is not that big, I would look that way. I have 99dB (Tannoy Westminster GR), 95dB (Tannoy GRF90 GR) and 89dB (XTZ Divine Alpha) speakers. All quite different types, and the Westminster clearly being the best speaker, but the XTZ Alpha sounds far better at lower volumes, and costs 5 times less. It also sounds very very good at high volumes actually, and in my view betters many 20k to 30k speakers out there... I highly recommend that speaker. It also has tuning possibilities to suit taste and/or room.