Keep an eye on the DSM compatiblity.
First generation DX6i were on DSM/DSM2 "frequency/programming".
Second generation DX6i used DSM2/DSMx.
The DSM are no longer supported, so finding new receivers would be difficult.
However being that both versions of the DX6i supported DSM2, it shouldn't prove an issue.
DSMX is the current supported programming for Spektrum.
If you want to change the mode, it is a simple matter of engaging or moving a spring.