I think it would be kind of cool if his xtreme was his only power with voice sounds. A one syllable word (like "no" or "war"), or a shout (like Wolverine in his boost).
Basically, what I'm saying is for it to be named like the word or just shout.
Well, at least that was what I was saying before I realized that neither Budhabear or cvc mentioned anything about needing either an idea for an xtreme or a name for it. The last thing he said was that he needed to fix the xtreme. So I'm guessing he's got the idea and the name already figured out.