Mining @ 640kh/s with 270x right now... Anyone using 270x here? Just want to know what would be the peak hashrate of it

I have MSI R9 270 @ 585 KH/s.
But it is old 14.4 WHQL without any tweaks in miner software.
I'm using mod 14.6.. Maybe I'm doing fine with my speed atm.. Thanks Randywald