I did a similar thing. I installed an internal Spektrum module and use Frsky in the module bay on my 9x. Frsky w/telemetry is an excellent system from a price/performance stand point. Combined with the 9x and open source firmware it gives me everything I could want.
However, I moved the antenna to the Flysky module to try out the Flysky receivers and they are actually pretty good. I tested the range on the ground and in the air and couldn't fly it out of range. I think it might be an good system for park flyers and such. The 6 ch receivers are pretty small and inexpensive.