I have personally found that 2 x 10's firing up worked best for me for daily driving. For all out SPL fire subs forwards and port to the side.
I wouldn't do 2 12's ported, or even sealed for that matter. A single 12 ported, or 2 10's ported would be your best route. Doing the 15 with that room might even be a little sketchy.
Any other questions PM me. I ran 1 8, 1 10, 2 10s, 1 12, 4 10's and a single 18 in my mustang hatch //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif Most were ported and sealed at one point in time.