RE: Great Planes Ultimate Biplane .40 Build. (The covering)
A good radio and good equipment is never a waste or too much. I use the Futaba T8FG expanded, with the free upgrade, to a 14 channel. As for the engine I switched over to gas a couple years ago and have not looked back, definately cleaner, more cost effective, and easier to operate. Batteries are your equipment's best friend, don't cheap out. I ran ni-cads until ni-mh came along and am in the process of switching them out for life's, life's are quiker charging and hold there power better. Nothing I use is what I consider the best or the macdaddy, only what I feel is one notch further than needed. In this hobby if your worried about the money you have already spent too much.
In summary, get what you want and is sufficient to do the job.
On a side note; I would not use old equipment, well I won't anymore. It cost more than buying new, eventually.