I don't know about atmos speakers, but I have found that the surrounds don't necessarily need to be "exact" voicing as the fronts. They need to be close in sound, but if you have go with a different manufacturer it is not that bad.
The front 3 speakers absolutely need to be exact same voicing and manufacturer. Otherwise, the discontinuity is easily noticed and will distract from the involvement of the film.
The front 3 speakers absolutely need to be exact same voicing and manufacturer. Otherwise, the discontinuity is easily noticed and will distract from the involvement of the film.