D6000 is customized India specific i.e only indian version of D6000 has 3D. Most other countries the 6000 does not have 3D. So it would not be advisable to go for that model as 3D is probably added as an afterthought and it not designed for 3D.
Coming to the D5900, i have seen it in showroom and it provides excellent 2D Picture Quality and the design of the TV is also pretty good and if you dont want 3D then that is a gr8 TV.