Besides the extra one or two accessories and slightly different 'finish', is there actually a noticable sounds difference between the three versions? Looking at the specifications the one has a 95dB sensitivity. Two has 96dB and Three has 97dB. Similarly, each have a 2kHz frequency response increase on each other. Does this add a noticable sound difference between say, the one and three? I ask because the one is £20 and the three is £40 and just interested in knowing if the price difference can be justified in terms of sound quality?