I was hoping some more of the Outhouse guys who fly RC would drop by with some advice but, here's some more from me. Don't waste your money on trying to upgrade the Super Cub. It flies as good out of the box as it will ever fly. It is strictly a first airplane. At some point in the future it will be to your advantage to purchase a Spectrum DX7 as you can program it to handle several different airplanes. There are new airplanes coming out all the time that are receiver ready. All you have to do is bind them to your transmitter.
RD
i was coming in here to say something similar. i have the dx5e, because i bought it when i didn't know better. get a computerized radio. that will allow you to fine tune things to your liking. you can't do that with the dx5e. i use mine on a cp heli, and it's totally the wrong unit for that. the jerk salesman made a sale that day, but he'll never see another dollar from me. live and learn, eh?
my advice would be to do exactly what you did to learn flight simulator. use google to find enthusiast forums. learn everything you can. the more research you do, the better off you'll be.
just remember that RTF rarely is, right out of the box. they always need some tweaking.
even more so with BNF. if you want true RTF, your looking at something like a litehawk zoom.
fine for some, but most would get bored with it pretty quickly. it's going to be as pedestrian as possible. otoh, the zoom is really cheap, yet durable. if you decide to try one, once you decide to move up, you won't have a ton of $$ invested in it. well under $100 for everything you need, and well supported. lastly, i would point out that without an ama license, your restricted to park flyers literally at the neighborhood park or open field somewhere. if you want to fly at a modeler's flying field, you'll need a license no matter what you fly.
man, you ain't just whistlin' dixie!