Sub doesnt sound loud

hi this was the first time i bought a car sound system i bought a monoblock pioneer gm7300 800 watt amp and 7500 mtx subwoofer . i got so angry because i spent heaps of money on this sound system and it doesnt even sound loud.

my friend bought a cheap $100 pioneer subwoofer and when i listen to his sub i have to close my ears from the vibration and sound