A DX6 is a "DSM1" transmitter. First generation 2.4 GHz. Not compatible to any newer DSM2 or DSMX generation recievers.
I believe there is no modern, cheap reciever that can communicate with it.
Ideal you'll have a BR6000 reciever to mate with it.

If you talk about the DX6i or simular, that should mate up with the normal series of modern 2.4GHz recievers.