The easiest and best step up from the Firebird Commander is the Aerobird Challenger. I know that you want to be able to re-use the radio, but the Challenger is such a great deal that you might want to consider it. The price is down to $109 and you can get it even cheaper on e-bay.

The Challenger is so similar to the Firebird, that you can basically fly it with just the throttle and steering, as if it were a Firebird. Then as you fly you can take your time experimenting with elevation inputs to get familiar with 3-channel flying. If you decide to go with the Challenger, start right away in the Pro-Mode. The Sport Mode just doesn't give you enough control to fly it well.

There are modifications that you can eventually make to the Challenger to keep your interest for months, and years, to come. It would be a great buy for you, particularly as you have a limited budget.