I'd disable the sub's crossover, or if that's not possible I'd set it as high as possible - the 1070 can take care of all the bass management for you, so the extra crossover at the sub isn't necessary.

For the Mythos 6 mains and Mythos 7 center (both of which go down to 60hz), you could probably run the crossover as low as 80Hz if you wanted, although it might be useful to experiment with 100Hz. I wouldn't go any higher than 120Hz, but it's not a bad idea to give it a whirl. I'm not sure about what Mirages you have, but you might try 100Hz as well as the 120Hz you're presently using.