[MetalMan]

Just FYI, I'm spinning my KMS 4120/6 (610 kv) to ~20,000 RPM max. at 10s A123. I'm sure this motor isn't nearly as good quality as AXI motors, but it seems fine. But as sikeston34m said, the switching rate could become an issue. I think that for a 14pole outrunner (what I'm assuming you're using), 25,000 RPM would be to the ESC like spinning a 2pole motor at 175,000 RPM. Unless my logic is wrong, that will take quite an ESC!