For around $50, Hitec 5625's would get the job done reasonably well. They are plenty of torque and pretty decent speed at 6 volts. They are not quite as precise as the 5900 series but they will do ok.

No kidding around, you dont want to be stingy on servos if you want to seriously fly 3D. Good equipment makes all the difference in the world in how well the plane handles. If you have the money buy good servos, they are definitely worth it. If you are on a strict budget that is one thing, but if you have the money you really will not regret buying good servos because it really does make a difference in performance, a pretty significant difference. [8D]