A really nice subwoofer. Deep, clear bass and it gets failry loud. My uncle has 2 of the 10" models in his van and it sounds really good. Could be a little clearer but for an all around subwoofer it is very nice. Crutchfield has a sale going on right now for these so you should check it out and get some.
The Kappa's are louder and hit a bit harder and do have clearer bass. Both are nice subs though. A JL 600.1 amp is a good choice depending on the enclosure that you will but the Kappa's in.
Well if I owned a Kappa I'd put it in a sealed enclosure. I'd put a 12" in a 1.0 cuft enclosure. This would give you very good SQ and the sub would get pretty loud. If all you want is loud, hard hitting bass then put it in a ported box tuned to 35 Hz. Keep in mind that if the sub is put in a ported box there will be no SQ.
not to bust ur bubble but if you want great SQ while having the benefits of a ported box, tune it to about 28-30 Hz - i have one for two 10's tuned at 29 and it sounds awesome
