What is the actual issue ? Can you not get bright enough photo's ? If you shoot in RAW you'll be surprised how much detail you can recover.
The main thing isn't the camera though it's the lens. Look at any photographer at a sports event and the physical size of the glass they've got hanging off the end of the camera speaks volumes for this. You need an F2.8 type lens, they don't come cheap though.
You can hire them, if you're going to a bigger indoor event hire one and see what the results are like.
Jimmy's photography on here is always stunning, he's done a tutorial on taking photo's as well, have you seen that ?
Clicky