Subwoofer integration with Silverline Sonata MK111

Until recently I was running a Sonata 2 with my Rel Stadium 2. Jax has good points, settings will be different with these slightly different models (The Sonata 2 used 2 x 10"s) as well as your room but you should get a SPL meter to help. By ear, in my particular room I found myself keeping the crossover quite low. I can't recall the exact numbers but I think I was only up about "1 click" on the coarse setting and possibly only 1 ( or 2 max) additional "click(s)" on the fine setting (at most). I always kept the gain quite low too... barely between the 9 o'clock and never much, if any, more than the 10 o'clock position. This was never overly noticeable on most music... on the occasionally very deep bass notes I felt there was a little extra help on filling out the lowest extension but it was always very subtle and well integrated. My emphasis was on what it did for locking in the image focus of the performers, especially the center image of a solo singer... the Rel, when applied as described, added that last bit of extra image definition in an absolutely uncanny way. My tip is to err on less is more...put on a track with some good low bass extension that has vocals too, when you can start to hear a plummy ripeness, you've definitely gone too far, back off until that's gone but your singer materializes more profoundly... there is a balance there you can find with experimentation. Be patient. Good luck.