I use a 10XL on my gorillamaxx e-revo and I haven't had any real issues with it. See some of our last basher vids on brushlessmayhem.com for video. I think I got some of the revo their.
It does run a little warm, but I just changed to a 22T pinion so we'll see if it lowers the temp any.
You could go with a 60mm medusa 2000kv motor in your buggy. On 4s it should have similar performance to the 9xl, while running a bit cooler and possibly adding a little runtime.