They are just so so, dont expect to shake the guys car next to you. I think they are like 200-250 watts rms, so thats not too bad for powering a small sub. If its just about trunk space, they do have these new subs, not sure what brand, that are only like 3-4 inches deep. They dont need a tremendous amount of box space either. Might be something work looking into if trunk space is your only concern.
As far as pre-made all-in-one subwoofers go, they are the best available. To rephrase, it's probably the best plug-and-play option. You could look into the one that has dual passive radiators (looks like 3 ten inch subs) and hang it firing down off the rear deck. I had a buddy do that in a Camry and it sounded very good- just not loud enough for my liking
<-----has owned several competetive SPL setups, so take my "loudness" relatively.
Have them demo it for you in your vehicle before you spend the money to buy one. The audio techs at the Best Buy near me did this and also demo'd a 10' bazooka sub by partially installing it in my Mustang.
I honestly did not like either of em enough to fork over the money to buy one. I ended up going with a MTX Thunderform box that only takes up a third of my trunk space. Way better sound than either.
But...who knows...the basslink may be to your liking.