In addition to the first post in this thread these posts made me believe that they should use the same driver but with different tuning (naturally due to different housing).
Unfortunately I've never heard any of the GR07 siblings myself but I do enjoy the XE800 a lot.
http://www.head-fi.org/t/726119/review-vivo-xplay-3s-xe800-mobile-audio-perfection/75
http://www.head-fi.org/t/698148/knowledge-zenith-kz-impressions-thread/720
Unfortunately I've never heard any of the GR07 siblings myself but I do enjoy the XE800 a lot.
http://www.head-fi.org/t/726119/review-vivo-xplay-3s-xe800-mobile-audio-perfection/75
http://www.head-fi.org/t/698148/knowledge-zenith-kz-impressions-thread/720