Yeah, C1E is a power saving state. Not very useful for overclocking.
What are you measuring those temps with? I'm getting those at 3.2ghz, 1.375vCore. CoreTemp seems to be the most accurate. I've got a Tuniq Tower, AS5, and the large side-panel vent on my Gigabyte 3D Aurora 570 so I can't see any other way of reducing the temperature without lapping the HSF (which I think I will).