Shadorne...How many bits you need depends on the size of the bits
I think you will find that the quantization levels in D to A and A to D converters are fixed.
16-bit A/D conversion has 2^16 discrete numbers, or 65,536 quantization levels in the full-scale...so it has a granularity of 0.000015 or 0.0015 % of full-scale (full scale is like +/-2.5 Volts peak to peak) or roughly a quantization of around 0.03 milli-volts.
Even if you get more lights on, the quantization interval does not change, as it is tied to the full scale capabilities of the chip.
Note that the Behringer is a 24 bit ADC/DAC so we are talking about 16,777,216 quantization levels or signal granularity of 0.2 micro-volts (again a quantization granularity that is independent of which lights are lit up on the box)
=> So relax and simply stay well away from clipping if you have a studio grade 24 bit converter, as it means you have heaps and heaps of "digital" headroom to play with the digital signals using digital filters. Playing around with digital signals/filters (such as boosting one recorded channel immensely) is a good resaon to have the vast dynamic range of 24 bits so studios obvioulsy want that....but in general this capability is overkill for home play back of music. (Thankfully 24 bit DACs are really cheap so many of us have them anyway, whether they are really needed or not.)