96 honda civic subwoofer box

Ok hope you guys can help out, I have an mtx thunder 1000D coupled with an mtx 204. My subwoofers are mtx thunder 6000 10" 8ohm subs- 4 of them. i built this box and it does not sound good at all to me. It's 4.25 ft3 1 chamber dividing a pair a subs. 2 subs wired to a 4 ohm load to each channel of the amp which says 1 channel but has two channels on the output side. Its a sealed box. It sounds really muddy but has good extension but when you turn up the volume it just sounds loose and sloppy something every dude hates. :) the Box is built to fire the subs toward the trunk and yes the trunk is dynamatted very well.  im wondering should i scrap this box and start over? or would it sound ok with ports? also if i start over with a new box do you guys recomend to fire the subs directly into the cab? i tried to do a little research but found nothing on which way to point subs for opitmal sound. is there anything i can do to make the box smaller? im trying whatever i can to make this thing work im looking to get tight hard hitting bass from it. 4- 10 inch subs with about 1500 watts should be enough to do it right? what am i doing wrong?

http://www.mtx.com/caraudio/archive/2001Thunder6000Sub.cfm     <--- subs specs

Thanks,

Mike V

Disconnect both speaker wires from the amplifier.  Twist the 2 positive wires together.  Twist the 2 negative wires together.  Using a 9 volt battery, touch and hold the positive wires to the positive terminal of the battery.  Now watch the speakers and touch the negative wires to the negative terminal of the battery.  They should all move in the same direction.  If they do not all move in the same direction, one or more of them are wired out of phase.

Tried it.. everything is in phase all speakers move forward i did notice though that the center divider that is supposed to separate one pair from the other is not very airtight does this matter? consider me a rookie box builder. I am going to try again with another box unless this one can somehow be salvaged? im thinking of a box of about 1.25 ft3 per pair of subs coumpound loaded one firing into cab and another sub firing towards trunk. idk give me ideas im looking for hard hitting tight bass. i have the ingredients im just needing professional input as to what what box sounds best. i listen to mostly rap.