ok I searched and nothing so here is my question.

what is the diffrence between setting up my subs upside down and stting them right side up?

I want to do the whole upside down thing but another question that rises is, how much air space is recomended for this type of set up?

Here is phoenixtc set up and I want something like that but less complicated.

 

inverting them is no problem. just don't figure in the woofer displacement when building the boxes.

 

and make sure that you reverse the polarity to ensure that they're firing in the correct phase...

 

not really true.

sometimes having the phase revered sounds correct. just toggle back and forth on either the amp or HU and see which sounds better.