Let me clarify a little with what I know.
The developer got the mW mapped for the various module during the early development of the DSM2 mod. Including the startup 1's and 0's that set the bit for the power output to conform to each countries regulation if I recall correctly. So those smart fellers really covered a lot of the bases.
Putting a RTF module into a Turnigy radio will not magically make the range more. Without antenna mods, etc. What you gain is 2 additional channels and the programmability of it. In the end, it's still a parkflyer module. Remember, the RTF is MLP4DSM. Stands for M
technology. It's considered a low power module and is great for the micro helis, micro quads that many of us fly.
Now, if you take the High Power modules from a HP6DSM, DX4e, DX5e...or even a DX6i...then you are going to have about the same range as those radios are rated for. HP6DSM stands for High Power 6ch DSM.
The module inside the HP6DSM is similar to the DX4e, DX5e and DX6i. With the newer revised version in those last three radio having DSMX capability. Which you also retain once inserted into the Turnigy 9x.
Putting a HP6DSM, DX4e or DX5e into the Turnigy makes sense because you gain the programmability and flexibility of the open source firmware. Plus many mCPX and nCPX owner already has the DX4e to hack up.