Hell, I have a dual 12" ported box sitting in my basement now. What specs do you need? It's 1.5 cubes per sub, tuned to 28Hz. Painted and carpeted, ready to go.
It depends on the builder at the shop. I bought one from HIFI Buys(tweeter) and it is built pretty good. My cousin was the shop manager at one on they other side of town and he built incredible boxes. It just depends on who the hire and how good they are.