IF wanted real subwoofers back there, they sell em. In single and dual 10's and 12's. Dual 12" subs requires a seat lift kit to fit. Which cost as much as the box. The rest do not.
2008 Lariat SCrew 6.5ft box. 120k miles.
White-sand chrome package on black leather, 3.73ls, pwr/htd seats, mem driver seat, pwr/htd/indictr mirrors, pwr pedal, sat radio, auto climate, moonroof, pwr rear glass, ext range tank, parking sensors, painted headlights.