Best at what?? Not in a specific order but all worth mentioning...
Kicker L7 you'll want atleast a 1500 watts... Solid Stillwater design and its own unique sound... Perfect for tight spaces and SQ sealed but can be a SPL monster ported right. ( don't use kicker specs
) have one of these in a car off a 2500 watt ZX amp..
MTX thunder9500 you'll want atleast 2000 watts.... Longtime player in the game and one of there top models... Ported it can move some air... I've only heard this, no hands on experience...
DC Audio, really depends on your "level"? 4 would be comparable I'd say to the above power and sound wise... Touchy speaker IMO.. But some just want it...
Sundowns sa15 is a solid 600 watt sub that can handle much much more and less expensive than some .. SPL woofer for sure.
Ascendant audio arsenal15 is also a good sub that can take alot of power beyond specs.. SPL woofer.
Audio ban immortal15 is a hard hitting SPL moster as well
had 2 of these in a blazer once with 4000 watts to each..
JL 13w7 is a 13.5 but a strong contender here in the 15" catagory.. SQ is top notch if that's what you want... Can handle 2000 watts and purrs but it hits hard as well...
So far I think that's all the 15" speakers worth mentioning for brain shaking bass.... This is just my opinion and experience...