Just gonna throw this out there to muddle your choices.
Consider putting the xSIID at the wrist/forearm location. IF (big if) the Power Bracelet becomes a viable option, you may need it close for functionality.
My suggestion: Implant the NExT, hang on to the xSIID, maybe skip the xM1.
My Better Suggestion: Follow your bliss, man. Whatever makes you happiest is the best solution for you. 