RE: Kit or ARF
Any brand servo will work with any brand receiver. It's universal these days. However you'll need a Spektrum Rx to go with the DX6i, and I don't trust those cheap orange clones enough to recommend one.
I wish the industry would settle in on a single 2.4ghz setup so that we can return to the days where a Spektrun transmitter, Futaba receiver, JR and Hitec servos would all work.As it stands to have to match Tx and Rx brands or they won't bind, or stick with FM.