In an LS, you honestly wont need more than one decent 12" sub. I had a thought of having 2 x 12" but then i scrapped that idea and just got a 12" pentagonal xplod sub. Now i know that sub isnt the best, but hell it runs really well off my kenwood amp. I am dissapointed with the sub now tho, it just cant exactly keep up, it starts distorting with certain music. If you have sum cash, then i would highly recomend checking out Directed audio studio subs. U can get a 12" dual voice coil and ive heard them and i tell you what, they are incredible. But it all depends on the system you want and how much your willing to spend.