I have a single 15LF Kappa as a subwoofer, built in the 'traditional' bass reflex. I wouldn't recomend it for use as HT/Home Music.
HOWEVER, they do rule for sound renforcement. The sub is SO loud (just one single one remember) the Mids (some inferior make) have difficalty keeping up (having said that, i do have a peavey CS800x bridged, driving it 1kw:) ) IDEAL for loud BarBeQ parties :)

My friend has a dual 18" eminence bin and swears by it