Actually, the core stepping difference can make a big impact on your warranty. Unsupported core stepping voids your warranty.
But i dont think that you need to worry about that.
From the website Bios Release Notes:
The new bios version 0047 supports the CPU E8500 with the new core Stepping.
You will see that the CPU E8500 with SL Number SLB9K has the CPUID 1067A.
So it is supported now with th new Bios Version. May be the website will be updated soon.