-3 @ 53hz is perfect for my bedroom system. The speaker location and listening position are fixed, both close to the front and rear walls respectively. This along with a small room, make for a boomy situation. Every small ported bookshelf I've tried was a poor match for this setup. Now I have a 4.5" sealed with a -3 @ ~74 hz, a little lean, but not boomy. I would like to try something deeper, but still sealed.
Thanks Ryan