Most live sound applications low pass the whole system at around 40-50Hz because A) it's not a brick wall filter, B) the info below that isn't easy to reproduce in a large space and C) in order to reproduce it well, the drivers and power are very expensive to buy and move. The low E on a bass guitar is tuned to 41.2 HZ if it's at concert pitch, yet what we hear is the first partial at 82.4 Hz, not the fundamental. If a synth is used, sure, you can get whatever frequency you want, but a live venue isn't considered to be a "HiFi" installation. Then, there's the issue of room modes/standing waves- has the space been well-treated to minimize them? Many have not. The school gym I just worked on has pegboard with fiberglass batt insulation above it, which does a good job for a lot of the reflected sound, but the response has some issues, mainly because of limited available subwoofer locations and the fact that the in-ceiling speakers weren't going to be moved, so they interact with the walls, ceiling and floor as they will but the response was still very good to the lower HP crossover region. It sounded very good with a lot of different types of music and pretty natural for voice over the mic.
You're worried about less than an octave with an amp that was never designed to be used in a home stereo anyway, and even though they share a common basic use, they're two different applications.
