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, Silver RX1; Martinlogan Dynamo 700, Marantz SR5006, PS3, Oppo BDP-103D
2ch Sony KDL-32W650A, Sonus faber Toy Monitor, REL T3, Marantz PM8004, Sony BDP-S1000ES, JVC T-X3 tuner, Apple TV, Peachtree Audio DAC•iT, Sennheiser HD598
pc Monitor Audio Radius 90HD, Audioengine D1, FiiO A1