it is all about flexibility. you can use a bunch of y harnesses to limit the channels, matchboxes as well but I think in the long run you would really be more satisfied with 8 or more channels. The 8103 or new futaba 8 channels would be suitable. after setting up one "advanced" aircraft on a computer radio, you will be adding channels/servos and throwing all kinds of mixes at your sport planes.

you can find some terrific deals on second hand JR 10sx and sxII radios. get a new battery pack and have it checked out.