The phase control will help with any delay in the lower frequencies , basically if the low end seems out of sync with the midbass and vocals.
The crossover will cut the frequencies above or below what u want the speaker to play.
The level control { IS NOT A VOLUME CONTROL } is there to match input to output levels.
Your alpine has a bass engine built in to help set up and a basic eq for the midrange.
If your stuck give me a shout.