I would go with the Futaba BLS servos. Choose which one you like. I run on my 808 buggy BLS351 for steering and BLS451 for brake/gas. Its said that brushless motor has 3x the life of regular. I haven't yet seen a dead BLS servo. My BLS351 is 1 year oled (10+ races) and no problems!
I ran it on XT8 for a season and it is strong and fast enough for a truggy! But if you think BLS351 isn't strong enough for steering, choose another BLS (speed for torque).
Use Lipo with high quality switching LiPo regulator. I would suggest Castle Creations BEC. Its programmable - 4.1 to 9.0 output voltage and supports 2S to 6S LiPo!
Another way to go is to use KOPROPO servos that support 2S LiPo straight, without LiPo regulator. Don't remember the exact types, but you will see from specs that "supports LiPo" or something. Most RX support LiPo already. So you can run without regulator.
JR is coming out with brushless servos also!