Im going to get a esc for my axial that has a bec of 5v.
Should i go ahead and get the external bec so I can get a full 6v to my servo or will i be okay.

Depends on what battery capacity you are ging to use.. If you use over 8cells or 9.6vlts you will definitely need a bec but if you are just looking to control the voltage to the rx then yes.

I was going to use a 6 cell 4400 mah pack.
So i guess i will get one.

Maybe I should have said, depends on what battery voltage your going to run. A 6cell is only 7.2volts you should good without a BEC with that voltage but if you want to controll the voltage to the RX then get one, but you dont NEED a BEC with that battery

But my servos will still be lacking some punch cause there not getting the full 6v?
I have no clue what im dealing with here.[&o]