I've run the Kappa's with the PSD 2002's and they sound fine to me. I've run them in both standard and pi horn applications. I've used quite a few of these drivers, and from the standpoint of someone with plenty of experience with them, I really can't recommend them for subwoofer duty. They'll be alright, you can probably get flat response to 35 Hz, but there are better options IMO.
Adam