JR and Spektrum are comptable, so while Spektrum makes up to a 7 channel transmitter (which is a very nice transmitter btw), the JR 9303 and 12x work with the Spektrum 9 and 12 channel RX's.

I use a JR 9303 with a mix of Spektrum RXs from the 6100 for my park fliers to the 9-channel RX's in a couple of planes.

You can actually do quite a lot on a 7-channel transmitter when you use things like y-harnesses, or even devices like the JR Matchbox that allows you to fine tune the throws for multiple servos working on a single channel.

Personally, between the Futaba and the Spektrum/JR for 2.4Ghz, I'd lean towards the Spektrum/JR gear. You can move your Nextstar over with just a receiver and trimming some plastic off of the servo connectors.

If you want to fly just about anything, the JR 9303 is a great radio, and all those BNF airplanes work wtih it of course. If you don't want to spend that much right now, get the dx7 or dx6, and you can upgrade the TX later and sell your old one later on.