I've been running JX Servos in both my 1/8 Truggy and Buggy classes and they've been doing really well for me at the club level with an occasional win over the past 7+ months I've been racing with them. I swear by their brushless servos, more info here:
JX servos are legit! - Electric Motors, ESCs, batteries, etc. @ URC Forums

You can probably cut some corners and go with a coreless, but if it doesn't say coreless or brushless on the side of the metal case, then I would stay away from the $13 servos.