I am not sure you are fully understanding what the Equal Loudness Contour is... This isn't about personal preference. Human hearing itself varies with volume. We actually "hear" frequencies in the 2-5kHz range as louder than other frequencies even if the actual volume levels for every frequency are the exact same. The lower the volume level, the more that 2-5kHz range stands out to us - thus the more imbalanced something sounds (sounds thin, flat and lifeless)
This is why many receivers' used to have a "loudness" button -- this was meant as compensation at lower volume levels. These days, there are other means of compensation for this -- for example, Audyssey dynamic EQ.
As an experienced critical listener, I understand how we hear so I expect to hear this imbalance at lower volume levels and as such, am able to compensate for it when doing critical listening. In other words, the first step is to understand that the speaker actually performs the same at lower volume levels and at higher volume levels.
With that in mind, speakers that offer high levels of detail typically do sound better at lower volume levels than speakers that aren't as detailed -- as they offer more clarity. Our 340's provide excellent detail