1: What is the Year, Make, and Model of the vehicle. 1990 Pontiac Firebird (T-tops if it matters)
2: What is your budget? Like to stay around 250 but im flexable for quality
3: What exactly do you want your outcome to be? (Good sounding music, or loud bass?) I want it to hit hard but not to hard (Sorry)
4: And specific sub sizes that you prefer more than others? I was thinking 12" but I have no experiance
5: How much trunk space do you want to use up? As much as I need to
6: What type of features are you looking for in a CD Player (aka Head Unit)? (Ex: USB, AUX, BlueTooth, etc) Must be USB and AUX, the rest is extra
7: What type of music do you listen to? everything but bluegrass
8: Is your stock stereo system amplified? (You may or may not know this) I don't know this
9: Do you have Steering Wheel Controls? (Volume/Seek on the steering wheel) No

I bought a 1990 firebird and fixed it (Love it so far still needs some work). Ill check this thread soon as I can, if you need any more information feel free to PM me or post here. Thanks in advance!

where do you want the box? sidewalls of the trunk? above the rear seats? built around the t-top holder (had this on mine)
what direction do you want it to face? up, forward, in?
stock stereo or aftermarket?

if you're building the box then around the t-top holder(removal is required) is best with them facing up. if you're buying it then you need to consider that each sub needs 1 cubic foot of air in the box.

http://www.sonicelectronix.com/item_46886_600W-Kicker-Autotek-Complete-Bass-Package.html

$250 for 2 12" subs+amp+wiring kit

box will be about $150 for this http://subthump.com/Pontiac-Sub-Boxes/FirebirdTrans-Am

or $100 if you use a single wheel well box for one sub.