How does it not sound right thus far? I always thought the Kans are really easy to mate sub wise. I never used REL before though. The only subs that I had problem with the Kans were subs with less than 15 inch woofers. They sounded boomy and clashed with the Kans smooth presentation.
If your woofer is less than 15", try turning the cross over point to its lowest setting then gradually turn the volume up.
If your woofer is less than 15", try turning the cross over point to its lowest setting then gradually turn the volume up.