But in reality, there are several parts that you should eventually upgrade if you're going lower...
Caster Camber plates because the stock ones aren't very durable, an adjustable upper control arm to restore the correct pinion angle, lower control arm relocation brackets to restore the anti-squat geometry, aftermarket struts and shocks to match the increased spring rate, and so on.
None of this is necessary to lower the car, but it is recommended.