The Kappalite 3015 (not the "LF" version) is an extremely versatile woofer. It will work well in an unusually wide range of enclosure sizes and tunings... so much so that it's pretty much always what pops into my mind when someone wants a very good 8-ohm neo-motor 15.
The Faital 15PR400 is sort of its rival, and is the smoother of the two, and goes up higher. It is also quite versatile as far as enclosure sizes and tunings, and is available in 4 ohms. Imo the Kappalite sounds more like a bass guitar speaker, and has a little more "thump" even though that's not obvious from the parameters. The Faital actually sounds a little bit louder to me when comparing them side-by-side, again something that is not obvious from the parameters.
I have used both of these woofers in home audio speakers as well as bass guitar cabs. I lean towards the Kappalite for electric bass, and towards the smoother Faital for high-end home audio.