Hi,
Please go in for the 40EX400
Its better than the BX400.
I know not much of specification changes but for that FM and some ambient sensor and the color of the frame.
I have been owning a 40EX400 for quiet sometime now and no complaints till now.
It looks awesome. no big difference with that lower frame in a different color.
I really don't know when the ambient sensor kicks in.
And i doubt the usability of FM on a TV.
Think twice whether you going to waste that much electricity in running FM radio on your TV ?
So basically not much of difference in both.
Pick the one which you think is worth your hard earned money.
Grey market option is also good enough.
You can get 40EX400 for about Rs 46000/- and plus wall mount Rs1500/-
You wont have a warranty.
But as usual capitalists in India don't give a damn in providing great service via warranty, so you can live without it.
!yr is hardly any warranty..
I did all the calculations you have been doing and i bought it.
So hope i was of some help.