7.1 is just a number to mark the number of speakers/subwoofers in the system's setup-- nothing else. 2.0, 2.1, 5.1, 7.1, 10.2 are all different speaker synergies, but they all can have overlapping qualities in soundstage. So basically, your average 2.0 headphone is still going to be 2.0, but it can try its best to have as good a soundstage as your average 5.1 speaker setup for your entertainment room. Just as a 'true 5.1' headphone with 4 drivers in each ear can have worse soundstage than a good pair of 2.0 headphones. Also note that the quality of the recording and mastering go an extremely long way in your perceived soundstage, as well as the type of music and its dynamic range.