Yes, if a signal is maxed out (0dBFS), a way to make it louder is to place said signal in multiple channels.
The signal is summed together, either by soundwaves in the air if you only use fullrange speakers or in the crossover of say an AVR.
In the crossover the low frequency content of all fullrange channels is summed together with the LFE and then outputted to Sub-out.
Therefore, you can have low frecuency signals higher than the max 115dB wich the LFE can have at 0dBFS, when played back at reference level.
In a 7.1 track you can potentially have little over 10dB louder effects if the same signal is encoded, fully maxed, in all channels.