Do I still need a subwoofer with floor-standing speakers?

For stereo music, many tower owners are satisfied without a sub. For movies, a dedicated subwoofer handles the deepest low-frequency effects better than most towers, which is why bundles such as the Klipsch R-26FA plus R-12SW package exist. If your priority is home theater impact, plan for a sub; if it's two-channel music, a good pair of towers may be enough.