Ok, i don't know anything about obsidian i will search some info..
For no reason i don't like alpine and i read the sa sub don't like sealed box and i don't have choice to go sealed, i want good sq so i read soundqubed is more spl??
I've actually got the perfect sub for you if you are interested. A 12" Soundsplinter RL-P Dual 4 (wires to 2ohm). Do some research on this one on here and you will find nothing short of great reviews. Excellent sound quality and gets plenty loud. Additionally, it works well in both sealed and ported enclosures. Send me a PM if you are interested.