what you really want for all the power any servo could ever need is an externsal castle bec. I use this in my moa crawler to power a power hd 31kg torque servo at 7.4v. The output voltage is programmable (set to 6v standard i think) and can supply 10amp. More than enough for any buggy
The difference was amazing in my crawler
http://www.heliguy.com/Extras/Electr...age-Regulator/