A fairly easy step up from a Firebird and still an electric trainer type can be either a Goldberg Mirage or a Sig Rascal. The Rascal is an ARF. The Mirage is a build it yourself type. I've tried both and they are very good flying models. If you insist on nitro power you can get the Rascal as a BIY kit and fly it with a 1/2 A engine. I'd suggest a Norvell .61 or if you are dedicated to speed a .74. The Rascal ARF comes with a motor and speed control and costs $169.95 from Tower Hobbies, freight paid. The kit version is less. The Mirage kit also has a motor included but no speed control. It could easily be converted to glow if you have any building experience, or you could probably get some help from fellow pilots or your hobby shop owner.