I bought Klipsch powered bookshelf speakers the R-51PM and I am in love in the sound they produce. Want to equip the. With a subwoofer from SPL series just not sure which one is suitable for the. Honesty I am leaning toward SPL-150SW because of the lower end of 18hz, but will let you do the talking on the matter. The room is 5x3.5 meters with clean wooden floor, one bed and one bookshelf. Everything is movable in the room so the placement of the speakers and furniture is not fixed. Thank you in advance.