I think the overclock.net forum has a vega bios thread where folks are pushing pretty high. I am at 1200 stable on an aircooled v56 flashed to 64 with just the 1200 SOC powerplay mod. I have another card that doesn't like it though.
I had the same thing going but the oc,d soc didnt like me tinkering with other stuff and i eventually ended up with a clean install.
Im gonna try the new drivers first this time, just to see whats even possible and if any luck come and replicate it on the BC driver with a SoC oc and so on