0.2L Vd won't shake the room at high levels, but is that the goal in a bedroom system? Will
any woofer make useful 20Hz, if peak SPL is 80dB?
@TankTop, perhaps you should add more details, such as main speakers, amp, room size, desired extension. If your goal is ~35-40Hz at moderate SPL from a smaller box (maybe 15-20L net), go for it. If you want more output later, make that box your secondary sub to address room modes, either in the bedroom or main system.