The KS series were fairly popular during its launch , primarily because people were looking at wrong numbers .
It was tested to reach 1400 nits + on test patterns but the picture fall flat quickly after , due to the TV's inability to hold the same level of luminance unlike the rivals , Sony's Z9D and X930E which can sustain the brightness level for a long time .
Its actual brightness level fall in the range of 400-500 nits ( which is roughly the same as GX800 ).
If you compare with the GX800 , the Panasonic TV has an advantage of dynamic tone mapping , more precise color reproduction despite not packing the quantum dots filters .
Samsung is still having problems to accurately control the large amount of colors from quantum dots layers .
Dolby Vision is also a bonus .
Considering the list of features , the GX800 is more versatile than the KS7000 .
Overall I would say GX800 is an improvement from the KS7000 , however small the improvement is .
IMHO probably not worth spending money just for the tiny upgrades but it is an improvement regardless , on the perspective of Picture Quality .