Getting bass right is vastly more difficult than getting higher frequencies right. You simply have to move more air and deal with the interference issues attendant to the omnidirectional nature of low frequency information. Powered subs are purpose built for the first job and allow placement flexibility for the second issue.
I think subwoofers are almost always just a better mousetrap
YMMV
I think subwoofers are almost always just a better mousetrap
YMMV