i'm using ace ds1015 servos for steering and throttle in my mtx4 that i from kelletts for around $130 each and am happy with their performance.
with features like:Coreless motor, metal gear, aluminium heatsink, 14.5/201.4 @ 6v torque and 0.108 transit time @ 6v, at that price these servos are hard to beat for value
kelletts hobbies 0296022333
you wont be disappointed