The SMS-1 doesn't offer particularly robust bass management for full-range speakers - you can get an 80Hz crossover for the left and right channels, but that's it. I'd probably leave the ICBM in the mix and connect the SMS-1 downstream of the SMS-1.

The SMS-1 will attempt to provide a unified flat frequency response - you'll be able to provide equalization to that mono sub signal so that the combined output of the Mirage and SVS provides a flat response at your listening position.