the Rel, which is a GREAT sub for music, will add a lot to your musical experience. Try crossing it over at 55hrz to start and go down from there.
I had a Rel B1 that I used with my Maggie 3.6R's (measured down to 34 hrz, about the same as your speakers), and I ended up with the sub crossed over at about 42 hrz, and not turned up too high on the gain, and man, what a difference.
I currently use a Def Tech Supercube 1 with my Maggie's crossed over at 40 (lowest setting), and once again, it's just sublime to add that sub for the lowest octaves.
Good luck.
I had a Rel B1 that I used with my Maggie 3.6R's (measured down to 34 hrz, about the same as your speakers), and I ended up with the sub crossed over at about 42 hrz, and not turned up too high on the gain, and man, what a difference.
I currently use a Def Tech Supercube 1 with my Maggie's crossed over at 40 (lowest setting), and once again, it's just sublime to add that sub for the lowest octaves.
Good luck.