A .40 LA is a good engine. And a four channel is a good radio.

To give you a personal account, I started with an OS .46 fx and a Futaba 6ch. I wanted some ability to take the next step after the trainer. The .46 fx has a good bit more power than the 40 LA. Both engines are very easy to use and very reliable.

I now have a Mustang with retractable landing gear and it's nice to have a 6 channel radio to handle it.

If I were to do it all over, I would get a Futaba 7C and an OS .46ax.

Your combination will be totally fine. But when you get a more sporty model with retracts or flaps, it's nice to have a few extra channels and a little more power.