An old thread, but I just went from an Sony BDS-P3700 to a BDS-P6700, and the the 6700 has far better video and especially audio quality, when played through my Onkyo A/V. The menus and remote are the same, as are most of the advertised features. The 3700 is probably fine if used with a cheap TV and playing through the TV speakers. But for home theater, the 6700 is decent, the 3700 trash.