As with most things for us as AMD guys , it is very hard to get a virtualbox working with osx.
However I did manage to get a working virtualbox installation some time ago, with this bootcd:
http://www.filedropper.com/empireefi <-- EmpireEFI FOR AMD
So what you are going to do : Download this EmpireEFI , Virtualbox and iATKOS S3.
For some reason this EmpireEFI is compressed into an self extracting archive, just run it and it will ask you where to extract.
NOTE: My norton says it is infected, however my Mcafee , Nod32 and AVG don't report anything suspicious.
So you will boot the bootcd, swap the iso with iatkos iso and press f5.
now select the iAtkos disc , type -v and boot it! no extra commands needed
after installation, you will always have to boot the HDD through EmpireEFI.
Hope this helps!