Need help with new system setup

I am wanting to upgrade from my jl10w3 to a deeper and louder 12" sub. I am looking at the HD12 from audioque along with there 1200D amp. My questions are what ohm should i get the sub set to for sq and everyday driving. What would be the best size box for the sub and i have never really been a big fan of ported boxes because they dont hit quite as clean as sealed. I was looking at this groundshaker box but not sure of the quality. If you guys have any other info that would help i really appreciate it i am so lost with all the tuning of boxes and what ohms and watts and rms my head is spinning.

Here are the links to all the products

http://www.audioque.com/HDC312-Copper-Coil-Subwoofer_p_23.html

http://www.audioque.com/AQ1200D-Amplifier_p_30.html

http://www.onlinecarstereo.com/CarAudio/p_27211_Ground_Shaker_CP112.aspx

Thanks in advance to everyone
Austin