It really depends on what you want. I setup for two different purposes. My track setup is relatively mild. I run either a 1515 2.5d or 1512 1.5y on 4S for racing and the same motors on 6S for plain insanity. 5S is sort of a middle of the road setup.

I've been running brushless long enough that the 2.5d on 5S doesn't impress me, although it still impresses others that aren't used to seeing it run. The 2.5d on 6S still impresses me.

TexasSP, just be sure that what you are asking for is what you really want. If this is going to be your first "good" brushless setup, you really do have to keep a couple of things in mind. This first is that the Revo (or really any nitro truck) isn't built to accommodate the power of a brushless system. The second is that you are going to wear parts out more quickly.

I haven't had much time for organized racing lately, so much of my running has been bashing either on the track or off, so most of my running has been on 5S or 6S. These days, I've noticed that I'm completely rebuilding diffs frequently. Very frequently. Ring and pinion gears are expensive. For the average guy that wants his truck (buggy) to be dependable, a milder setup is usually in order.

Another thing to think about is the battery configuration that you've chosen. One of the big things about going with higher voltage is efficiency and the related reduction in heat. I've done quite a bit of experimenting with 4S, 5S and 6S configurations. I have more motors and speed controllers sitting in my shop than some people will own in a lifetime. I've found that with the better equipment such as using Compro controllers with Neu motors (both of which run cool in the first place) running higher voltages isn't always necessary.

Personally, for most circumstances, I think that 5S is enough. Just yesterday, we were running a Neu 1512 1.5y (1900kv motor) on 5S with a Compro controller in an XT8 at the track. This is a nice setup. Very smooth and powerful with good temps. The controller just decided to self destruct for no particular reason. I've found that this is just one of those things that happens every once in a while.

Not knowing whether the controller just went or if the motor went and took the controller with it, we dropped a 1515 1.5d (2700kv) in the truck with another compro and ran that on 4S. It ran great. The temps were a little higher, but nothing to be concerned about. We even ran it on 5S, but it was just way too much.

My point is this...6S packs are expensive and you may not need all of that voltage.