Not familiar with 320 but on some aircraft models landing gear is almost as effective speed brake as spoilers.
Below 200kts the gear is much more efficient than the speedbrakes for slowing the aircraft. I often select gear down before flap 2 because the drag from the doors is remarkably effective (until they close).
Speedbrakes are next to useless at low speeds; the drag is mainly induced due to alpha increase than anything else.