I think you will have to update the BIOS. Most likely if you buy a board you will get stock that was made before the 6300 came out. I had to update my BIOS on a gigabyte 990FX UD3 board for my 8320 (I bought both soon after the 8320 was released. Actually the 8320 "worked" but I was worried some things might not be supported correctly without the new BIOS.
It is pretty easy to use one of gigabytes tools to upgrade your bios though.