I just had a 1Dx from Canon for a week. It's the finest Canon body I have ever used. Shooting at 6400 provides excellent quality, and 12,800 is still very, very good. Focusing is superb, too. They've made enough little tweaks to everything that the camera stands head and shoulders above my 1D Mark IV's. It was really hard to box it up and send it back to CPS....
If you don't feel like spending $7000 on a camera, then 5D Mark III has similar high-ISO image quality at less than $3K. Heck, my 5D Mark II does pretty darn well at 3200 and at 6400 is no slouch. I don't feel any qualms about shooting 6400 with either the Mark II or the 1D Mark IV when the need arises.
All that said, you may be able to get a lot more bang for the buck with a faster lens. What are you shooting with now, and what sort of events are you trying to cover?