well the reason i think the 70gx2 is 6bit, is i have a 1770gx which was the panel before it (i think the only difference is slightly higher contrast ratio).
the big selling point of the 70gx2 and the 1770gx, is that its the glossy screen so it is very high contrast. i had an 8-bit panel before this, and honestly the 1770gx is nicer to look at (had a planar pl201 before). that said, i'm not super particular about colors.