AMD Phenom II supports these instruction sets; x86, x86-64, MMX, SSE, SSE2, SSE3, SSE4a. So as long a the instructions you wish to assemble are found in those instruction sets, you are good to go.
There is no differences between Intel and AMD versions of the instruction sets.
Note on bootloader/kernel programming: If you doing "environmental" changes to the CPU (such as; setting up a specific memory model, paging or execution method) there might be some architectural differences between AMD and Intel. I don't think there is, but someone more knowledgeable on kernel programming might be able to answer this.
Thank you.