Which language is best for highly used web apps?

I'm a PHP developer by day, but I'm interested in moving to something a bit more 'hip'.

I work on web apps and am constantly seeing all these "PHP BLOOOOOOWS!" threads - but it handles what I throw at it just fine.

That said, I'm about to start working on a project that's not even been publicly released yet and the servers are getting some serious strain due to tapping into some live feeds from certain sites.

Once more users start coming on board, it's gonna be a massacre of epic proportions unless I move to something a bit stronger.

So, what should I be looking at for a data heavy web application?

Ruby? Python? Visual Basic? ;)

Gracias in advance, my fellow developers.