I have the exact setup in my MAXX 2.5 with the Big Joe's on the Velocity 6's. I stepped the servo up to an Airtronics 94357, which sells at Tower for like $109, and it has like 120oz torque, and is very very fast! I have it setup on a Pro-Line servo saver unit (about $45), and it turns those 40 series wheels/tires very sharply, all the way gassing them through the turns! I am very happy with this setup. I think the Air servo you're reffring to it possibly the 94358, 1 step up from mine, which has more torque, but is not as quick.....both sell at Tower for the same price. So you choose, either a little less torque (still very strong) and more speed, or more torque, less speed!

You will need to upgrade that flimsy little white plastic servo saver that comes stock in the kit! I was checking out Unlimited Engineering's stage 4 servo saver, which sells for just under $100, but really the Proline has all the same features as the stage4, except the arms are not alum alloy.....everything else on the Proline is adonized blue which looks great, and of course it is all ball-bearing action!

Just my recommendation, this coming from someone that uses this setup, and has great results!