It should be fine - while the 7700 has enough power that you could theoretically over-push the Atoms, in reality it would take a very extreme volume level and some unusual source material to deliver that kind of power to the surround back channels (probably something like 7 Stereo mode and a pink noise test tone played at a notch or so above deafening). In day-to-day circumstances, the extra power means that the 7700 will never clip, and clipping due to insufficient amp power is actually a more common means of damaging speakers (especially surrounds) than the scenario I described above.