Just to add my experience, we have had multiple issues without DX6i's. Binding and failsafe issues mainly. Strangely some combinations of TX and RX work and others don't.

But as for going non spektrum, it seems sill to me to spend £500+ on a robot and then control it with the cheapest TX you can get. Its your link to the machine and if a £50 TX fails you could loose a substantial amount of a £500+ robot. There are TX's from Hi-tec and a few others but Spectrum is the most common.

I would get either a DX5e with one of the known working orange receivers or do it properly and get a DX7S which people seem to have better luck with than the DX6i's.