Best SQL subwoofers on the market?

Hi, I’m looking for some SQL subwoofers, preferably two 12" subs. My budget is 0, but I would still have to have money to purchase an amp to power them, so I can probably spend about 0 on each sub. Trunk space is pretty large; it’s a 2003 Mercedes-Benz CLK 500, so basically the trunk space is similar to that of any 4 door BMW. (about 16" high, at least 4 feet wide, and about 3 1/2 from the back seats to the edge by the bumper.