I purchased the JR Z9100T and Z9100S for my 09Spec XT8.
$130 each and I highly encourage you to also upgrade to a larger capacity hump pack.
Another note of encouragement when using the high torque servos is be particular in your end point adjustments. Before I installed my servo savers I turned on my radio and dialed back the endpoints/travel rate a lot so the initial turn-on wouldn't break things....
Conversely, do you really want to send your $2000 machine out with only a cheap servo as your only means of controlling it?