with that power, probably go with the two S15L5 subs.
loud and low
that will depend on a number of factors firstly if you are limited on space then go for the L7 because the enclosure volumes will prob be close to the same for an L5 and an L7. but if the space is avalable then go for the 2 L5's i think they will be louder than the one L7 with the same power. but you also have to take into consideration that the L5 is a more of a sound quality sub and the L7 is more for spl. thats what kicker says i cant say because i haven't heard either of them. also unless you are dead set on buying them or have already you might want to think about some different subs. square subs have problems with stresses on the cone and surround. and sound quality isn't the highest. i personally don't like square subs and there are definitly better subs out there for the same price