I thought I share this moded bios for this MSI model (http://www.newegg.com/Product/Product.aspx?Item=N82E16814137024)
You can play around with GPU, Core clocks. My cards would crash on anything lower then these setting, but I saw people go down to 890 mv without no problem at GPU.
Just flash with atiflash. Use latest drivers.
Haven't tried dual mining, but I am sure it just works fine.
if you have questions feel free to ask.