4th order box with port thru rear armrest or factory sub location

[Deeavia]

i have a 2k10 CTS, and i was thinking of a 4th order box build for the 12in Alpine type R subs. any help will be needed. i have alrady removed the factory sub. i would like the port to fire up, if all possible. looking for the best ideas to use that will give me some loud and hard hitting bass.

please chime in with something. help a noob out.