Yes, you can use digital servos with the Spektrum systems. In fact it is better to use digital servos. The Futaba FAAST 2.4GHz is a little faster then the Spektrum. The price of the Futaba receivers are a little more then the Spektrum. The Spektrum receivers are smaller then the Futaba receivers especially the micro Spektrum receivers. You can use digital servos with any 2.4GHz systems.

Take Care,
Cheers, Patrick