Actually, since you're new to RC's, I'd stick with the servo you have in there right now. I think stepping up to a servo like the aforementioned airtronics or a good servo like a z9000s from JR would be more of a hindrance to you right now. Most people new to the sport don't have the reaction time to even notice a difference from a high speed servo. After you've been running for a bit and can stay between the tubes and maintain good control of your car, then consider stepping up to a high speed servo. But if you just have to have one, both of the servos already mentioned are great and the JR z8800s or z9000s are excellent as well and KO Propo has some excellent units too.