I was re-building SA's at one point but I ran out of motors to use. On topic, the Obsidian 12's at $138 are a force to be reckoned with. The specs speak for themselves and the only woofer that edges them out in terms of all-out SPL is ~40% more money per woofer. And yes if the OP is going with 10's then the OA option is out.
(pssst, three 12's will work well like I said in my previous post - less money than four 10's and the enclosure volume will be there to tune in the very low 30's to get that solid extra low end)