You may be better served posting these questions on an EU-based forum, as this place is geared towards the North American market. Model lineups and branding vary heavily from region to region. For example, Panasonic's 2013 NA lineup, from worst to best, went X60-S60-ST60-VT60-ZT60. There was no GT model for 2013 here. Other series (ET, DT, WT) are used for LED models and not plasmas. They also do not use the Prime and Next designations in their marketing here, but Reference is reserved for their best models. My best advice is get one while you can if they are still available in your region, as there will be no new plasmas from Panasonic for 2014 or beyond.
ht Panasonic 60" ZT60, Monitor Audio: Silver RX6, RX Centre, Radius 90HD; Martinlogan Dynamo 700, Marantz SR5006, PS3, Oppo BDP-103D
2ch Sony KDL-32W650A, Sony BDP-S1000ES, Marantz PM8004, JVC T-X3 tuner, Monitor Audio Silver RX1, REL T3, Apple TV, Peachtree Audio DAC•iT, Sennheiser HD598
lr Panasonic 50" ST60, Sony BDP-S5100, Apple TV
pc Energy CB-5, Audioengine D1, FiiO A1