The Kappa 6.5' commponents are the ones that cut out below 400 HZ (in my car). After all, they aren't subs so it works for me. My 12" Kappa Perfect sub works great and seems to cross over to fit in nicely with the 6.5" Kappa's. I'm happy with both.

Got some useful info. here...

http://www.carreview.com/Speakers/PLS_1805_730_50crx.aspx