A BEC will be cheaper most likely, though there are alot of good, strong servos that dont cost a fortune ( clicky ). Either way, your current servo will never work very well on just ~6v, it has to have more voltage..

I don't want a cheap/budget servo.
Will a bec solve my problem or how do I give the servo more voltage?
I want this to work, I don't want a new servo, yes I change my mind quick..
Thanks Neil

The BEC will solve your problem, just make sure you don't hook up 7.4v to your Rx unless 1. your receiver can handle it, and 2. you disable the BEC coming from the Mamba Monster by pulling out the pin on the red wire. (:

Receiver:http://www.spektrumrc.com/Products/D...rodID=SPMSR300

How do I choose BEC? CC have two.. I believe CC BEC is enough for me, I have 4s.

http://www.castlecreations.com/suppo...user_guide.pdf

My servo is a HV servo I think.

Doesn't look like you'll need a Pro. a regular CC BEC will do fine. (: