ORIGINAL: jagnweiner
I wouldn't say you need to spend the extra money at this point if you don't want to. I would recommend that you get a computer radio, however. You may not think you need 6 channels because you don't plan on flaps or retracts. There are several advantages to a 6 channel computer radio that you will use: end point adjustment (using the transmitter to precisely adjust how far your servos move), exponential (makes control surfaces less sensive near the center while retaining wide range of motion) and dual rates are a few. Most important in my mind, however, is the ability to use dual aileron servos without a "Y" cable. Many sport planes today use dual aileron servos, so this is a vital feature.
A good entry level computer radio is the Futaba 6 EXA. It is about $160-170, so it is not much more than an entry level 4 channel.
When looking at radios also try to find those that support MULTIPLE "Model Memories".
That means that you can set up the radio for multiple planes and merely switch configurations on the TX at the field... ideally coupled with digital trims or the like.
If you do so with a multiple channel radio, it will serve you very well for many years. It will also save you the extra cost for all of these goodies, over and over again, as you'll only need one radio... It's also one less thing to have to carry with you when you go flying.