Very nice series and stunning male.
To me it is more likely a Rufous-bellied Niltava because of the lack of pale base to the lower mandible ( that seems to be diagnostic at least on 1stW bird), the entire uniform rufous underpart from lower throat to undertail coverts, the irridescence on the lesser covert and the overall structure of the bird with a rather big head compare to its body.
All the best,
Jonathan