If you get a Sanwa system you will be one happy camper!

I actually do belive the MT-4S is 2S LiPo compatible. Well you can without any problem use a 2S (2cell) LiFe battery in your car as they do not fry anything. But remember if you do chose to go with the LiFe option to get a digital charger that can charge Lithium chemistry batteries. Another thing to remember is to get a battery with as many mAh as possible.
The more mAh the longer runtime you get.

I forgot to link to an accessory you would need if you are planning to get the charger i linked to in my previous post.
This will come in handy
http://www.hobbyking.com/hobbyking/s...apter_Set.html

And should you get some 2S LiFe or LiPo packs these will be good to have as well
http://www.ebay.com/itm/10pcs-JST-XH...item2eb807c817

Last but not least one of these can save your home from going up in flames when charging lithium chemistry batteries
http://www.ebay.com/itm/RC-LiPo-Li-P...item3a94543734

Just ask if there's more that pops into mind.

You've pointed me in the right direction and its much appreciated!

Anytime mate anytime.

So...

Have you received the WR-4401's you ordered yet?

YES! I'm really happy with the servos! I really appreciate your recommendation!

Glad to hear it, I like to share what I belive is awesome.

A quick tip, if you experience brown outs, then get a good external BEC, one you can program. Like the Castle Creations 10A BEC.

I put one of those CC BEC's in my Durango DEX408 V1 after I had installed an Xpert WR-6601HV servo.
The RX simply browned out, when I turned super rapidly, from side to side at max angle. (Not something one would do while driving of course) But still I like to be on the safe side, so nothing will interrupt the power to the servo as it is now.
I set the output from the BEC to 8.4V, which is what the WR-6601 is designed to handle as it's maximum operating voltage.

Will definitely keep that advice in mind. Again thx a mill!

Glad to be of help.