AD, I don't know why you suspect that you may be "missing" something; what you report is fairly typical. That 98dB peak uses 10 watts or a bit less for the M80s. The overall volume attained at specific volume level settings varies with the strength of the input from the source materials. Pre-amps typically have a gain(fixed, as is the amplifier gain)on the order of 15dB.
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Enjoy the music, not the equipment.