You would have to recone all four in order to have subs with the same t/s parameters since there is not a drop-in replacement recone for that sub. Honestly, I've heard the soft parts on those were shit despite its 4" coil. However, if you're dead set on having four, there were a pair of tens for sale here recently with the splw15 motor. You could use the motors from yours and those to have four identical subs.
I'm not really dead set on them I do love them but I also figured it would be cheaper. To get just two more than buy four of a diff kind but I haven't had any trouble with them at all besides a lil coil rub. When they were new I reglued them and haven't had a problem since