Building box for an SUV

Hello everyone. I'm new here, someone on blazerowners.com mentioned the site and I am glad to have found it! From what I've read here it seems like everyone is very knowledgeable. I am new to car audio, but definitely want to learn. I am putting together a system for my 2001 Chevy Blazer and I would rather take the time to learn what I'm doing and be able to tweak and upgrade myself than pay someone else to do it and have no idea how it works. I've been talking to a few people I know who work in car stereo sales and installations and doing a lot of reading, so I've narrowed down which components I'm getting.

At this point, I am just trying to figure out the best way to build my sub box. I am getting two 12" Polk Momo MM124's and I want to build a sealed box to go in the cargo area of my truck. The way I am going to set it up though is to have to seperate sealed boxes and use the space in between for an amp rack. What I am trying to decide is whether I should have the subs firing toward the tailgate or upward toward the roof. If I understand correctly, firing toward the back will be louder, but firing upward will produce crisp, cleaner bass (which is what I am looking for). Secondly, if I do have the subs firing toward the back, the subs will fire slightly upward in a wedge-type box. Does the angle they fire at make much difference? And if a traditional wedge box is like this |_\ would it make any difference to shape it like this /_\ ? Sorry for the crude pics.

Finally, is bracing necessary in this setup? If so, could someone please exlpain or link a pic of how the bracing is done?

BTW, I forgot to mention I am planning on making the box from 3/4" MDF. I want to spray the inside of the box, what to you use for this?

Thanks in advance for all the help and for your patience with my long post! When I get this all done, I will get some pics up.