To try to clarify the above post...

In the 2.4 realm, you are stuck purchasing receivers from the manufacturer who makes the transmitter.

JR and Spektrum are basically the same company, so you can use Spektrum and JR receivers interchangeably.

If you purchase a Futaba 2.4gHz TX, you'll need to purchase only Futaba receivers, likewise with Airtronics, etc.

The DSX7 is basically a Spektrum DX-7 WITHOUT the timer feature. You may want to consider the Spektrum unit instead.