wait you got a kappa through best buy? Last time I checked we cant get kappa stuff, only the reference.
You also have a center channel? Can you get pics of how yours is set up?
This tuned sealed box you speak of how did you accomplish tuning it to 50 hz? and if so, why 50 hz?
If it is in fact "tuned" to 50 hz, then you probably would have been better off going with a smaller 8" sub or low wattage 10" sub in a small sealed box, since the tuning of the box you have now would not play lows very well at all.
-steven-