Still won't be enough room.
1 X would more than likely out perform both of the L5s if given a proper box. 2 Would murder them without a doubt. You will not be able to fit either one of those setups under the seat however. Take it from someone running Solo Xs in an extended cab truck, lose the back seat and wreak havoc on the truck. Get 3000-3500
watts and upgrade your electrical (search function is your friend). Try to get from 5-5.5 cubes per X after displacement (taking out for port and about .3cu per sub). Port roughly 18 sq. in. per cube for the X. Your friend will be jealous.
Oh, and OP; if you are in the market for 2 Solo X 12s I happen to have a pair for sale.
Solo X 12s D4