I know that the ST60 can get brighter than the VT60, as for being the same as the GT50 I'm not sure, maybe. But If the VT60 didn't impress you, being a higher end model than the ST60 I don't think the ST will either. Hopefully you can compared them where you can get them for the same price.
Media room- LG 4K OLED EG9600, Pioneer Elite VSX-90, Samsung 4K K8500, Klipsch Gallery G28's, Klipsch Sub 12, Klipsch RS-52 II, Optik HD cable
Living room- Sony 4K 79XBRX900B, Onkyo RC-360,HTPC, Klipsch Reference R-62II, Rc52II,PS4
Gaming room -Panasonic ST60, PS3, Wii