Need a suggestion for a good zoom lens, I'm using the 55-250mm and I do a lot of indoor shooting. Today was probably the 4th time this year I shot pictures at River Rock

This is a picture I took of my friend tonight @ river rock, The noise performance of the 7D isn't horrible especially @ 3200 ISO (this was uploaded onto facebook, it looks a lot better on my laptop!)
It was hard to keep up with a low shutter speed cause my friend was the only one who did a rock & roll routine -_- So I had to throw it on a 320 speed if I remember correctly as opposed to 120 ish for the other contestants.
Anyways I definitely want a sharper zoom lens with possibly more reach. The only ones I'm more familiar with are the canon L zoom lenses but those are about 4x the price of my current one :/ Any suggestions? Or should I just get an L?