I have a 03 350z, live in cincinnati ohio..

budget?
what's the purpose of it ?

budget. around the 3-4 range as far as the purpose just listening to music. Rap mostly and some rock!

hundred or thousand?

if hundred for now you'll be getting a head unit and new interior speakers. sub/amp/box/wiring usually cost $300 themselves for okay stuff and you don't want to get them first unless you want to hear nothing but bass.

hundred, I have a head unit that has navagation just need the speakers and wires! Sorry i havnt been very clear!

http://www.sonicelectronix.com/item_44472_MB-Quart-ONX2.100.html
http://www.sonicelectronix.com/item_63983_Pioneer-TS-W310S4.html
http://www.sonicelectronix.com/item_951_Single-12-Sealed-MDF-Subwoofer-Enclosure-Belva-MDFS12.html
http://www.sonicelectronix.com/item_67790_Rockford-Fosgate-R165X3.html 2 sets of these.
http://www.sonicelectronix.com/item_39877_The-InstallBay-AK4ANL.html


how you will wire it

id like to get the speaker box that fits flush under my back sway bar..

something like this.. http://www.amazon.com/Zenclosures-Nissan-350z-2-10-Subwoofer/dp/B00D8GZUPS/ref=sr_sp-btf_image_1_6?s=electronics&ie=UTF8&qid=1373510873&sr=1-6&keywords=350z+speaker+box

But you said a 12 inch sub.. i think only two 10 inch subs can fit back there..

http://www.sonicelectronix.com/item_63985_Pioneer-TS-W260S4.html

then get one of these.

with your budget you can't afford two subs.