Another option for better speakers/bass for music is a 3-way with a nice woofer to that effect, if one is thinking dual systems, or even a convertible system without the need for multiple purpose subs. I had been experimenting lately using my Fusion-12 Tempests (albeit it a 2-way design) with lower crossover (60, instead of 80hz) because, that eminence Delta Pro 12" woofer is a mid bass beast. That displacement (I don't know why I stray from this notion) thing again. In this instance, the mid-bass capability of the larger woofer lets me focus the subs as fill for the lowest frequencies with music.
Second is, an older set of JBL 3-way with 12" woofers that reach down into the mid 30's. Really a noticeable difference in the 80hz and up range. The bass is very articulate and uncluttered (uncomplicated, at least), if that makes sense. Double bass struck, or with a bow is phenomenal. The "toom-toom" sound that goes right through you and makes you play well recorded bass loaded tracks repeatedly. Right now I have on Tsuyoshi Yamamoto Trio ( Most excellent jazz piano, double bass and drums from the "Three Blind Mice" label) marathon and it's eating me alive, and this with just acoustic bass! I can do this with the subs too, but it is just not necessary in this case.
I have a very capable pair of Dayton, Reference Series, hi-fi sealed, 12" subs, connected to a dsp amp. I can get some great musical bass from these. In their sealed configuration, they too reach to the mid 30's, even though frequencies down to 20hz can be felt. I think it is the lack of compromise with being able to disregard the lowest frequencies that help here. I also notice that the Reference drivers are a lower Q and lower xmax than the Ultimax. These particular subs have a higher frequency reach than what is typically used for HT types. By comparison, my Ultimax does not do the music as well. Not as noticeable unless I start using subs with bookshelf type speakers that are sub-reliant. The larger woofer speakers I own tend to mostly cover for the subs when needed.