A 'normal reasonable listening level' is as far as I'm concerned, somewhere about 80dB or so, give or take about 10dB. Your next question will surely be 'how do I know what level I'm listening at?' Without test equipment to measure the noise, you'll need to make a mental comparison with noise in the environment with which you are familiar.
One thing I'd like to quote from here is this: " ... (Office) Noise levels can be reduced by encouraging workers to not play the radio continuously ... It has been determined that continual exposure to sounds at or above 80 decibels will cause permanent hearing damage. In such environments, special precaution must be taken. Walls, ceilings and floors should be insulated, and workers should consider wearing noise-reducing earplugs, sound-muffling headgear or other apparatus."
That's clear to me. It means that the the traditional BBC/Harbeth monitor speaker design target for listening loudness at around 75-85dB is correctly chosen as the upper end of the advisable long-term exposure level for safe listening. Many other speaker designer would probably say that 80-85dB was at the bottom end of their imagined user's listening level which as I've shown has implications for subjective bass performance and long term hearing damage, certainly in rock and roll recording. As I've said before, the consumer should really dig in to the question 'what listening level were these speakers designed to be listened to at'. Call the sales department and see what they say. If they say something much above 85dB remind them that they are encouraging hearing damage. If they can't answer the question, it means that they don't appreciate how the ear (or the law) works and their speakers will almost certainly be bass shy. Monitor speakers proudly promoted and marketed to recording studios as opposed to broadcast studios sound thin at home at a lower level because they are optimised to be thrashed to sound normal at 100dB++. Recording studio monitors are really unsuitable for domestic use because they do not sound rich, full bodied and believable at normal domestic (moderate) listening levels - I showed why on the last post. Broadcast monitors are eminently suitable for home use because the listening environment and listening level (and room size) are very similar.
Attached a chart of typical noise levels. I've marked what we consider to be the moderate, sensible, normal level in green between about 75dB (male speech at 1m) and heavy road traffic at kerb side (85dB). I explained why in detail on the previous post. Believe me: hearing-damage litigation is set to explode over the next years as a generation of deaf youngsters reach middle age. A Harbeth is a speaker solution that does not need and is not designed to be hammered to sound absolutely natural.