I'm new to 3D flying and don't really know what's out there in terms of servos. I've ordered an Airfoilz Edge 540 and am looking for something stronger and faster than an HS-55 that has replacement gears available and is not too expensive or heavy. I would rather not pay more than $20 per servo. Also, does the Edge 540 require two aileron servos?

Which models should I be looking at?

In my Airfoilz, I use HS-65's...very quick, nice centering...and yes, 2 aileron servos, one per wing half

Thanks... I've just spotted this servo on Tower - this would do the job in hand, right?
http://www2.towerhobbies.com/cgi-bin...&I=LXDTB5&P=ML

Yup! They will do just fine.

Might be too costy for you, but Graupner DS281 are nice, and DS361 rocks.