Audio Systems: box, 4x6 speakers, speaker boxes

Question
this may be small but I'll ask--I drive a fork truck to pay the bills I am limited to room and have to install my stereo up top in the cage.I have a stereo out of a 99 neon and I have made some speaker boxes for 2 polk 4x6 speakers--the boxes are 6x6x3--I am wandering should I put something in the boxes to fill up space or would I be better off without--or-- would it not make any diff? Thanks for any help and or info

Answer
Bill,

 somethings depending on the speakers the boxes will be filled to cut back on the echo' affect the box can have with some accoustic waves... in your case i'd stuff them with quilting material to try it out then empty and pick your best sound quality , it really depends on the speakers and type of music you listen too ... hope this helps you out

thanks