What camera lens should I take to a crazy concert?

In a month I'm going to STS9 (if you don't know this is a band like Bassnectar, Pretty Lights, it has that dubstep feel, electronic music) and the concert will obviously be CRAZY.

I have a Nikon D300 & want to know what lens I should bring…

I have an 18-200mm f/5.6

and

50mm f/1.8

BUT should I invest in something else for the concert?

The zoom would be nice but it is too slow for the lighting conditions, I'd go with the faster 50mm lens. If you're feeling rich you might look at a fast wide-angle fixed lens like a 28mm f1.2 for this type of use. You'd get some great shots.

If it's a crazy concert, don't bring a dSLR. Get hold of a point-and-shoot camera and go crazy partying instead.