Ok let me make a point clear , head unit plays a major role.
with your head unit you cant expect show off kinda.
I said square box of 7 cm, so depth and width is 7 cm i suppose.
Keep the equalizer in head unit as flat
I mean you say gain by cross over. keep the gain in minimum position.
Try to increase step by step , my advice do not go beyond 25% to 30% of gain.
keep the switch in lpf .
Then in the eualizer , change the output , keeping just few pts in bass must help further. too much will spoil.
Very much important
FOR TESTING PLAY A GOOD REAL BASS MUSIC.
EG IN TAMIL OLD ILLAYARAJA MUSIC LIKE MEGAM KOTTATUM HAS PURE BASS. REASON THE BASS IS TRUE BASS BY DRUMS. nOT KEY BOARD BASS OF TODAYS MUSIC.
hope this must help your set up.
For show off , you must need a a good head unit , may be from jvc as it has low price with good output , a powerfull mono amp , a ported sub woofer box.And very much important is good wiring ,
could be detail in what you have now with pictures .?