Personally, I would want a NeuroPsychologist to do the testing, given all the factors you've got going on. An experienced neuro should be able to pick up on anything impacting his test scores.. plus, they do a lot more than just IQ testing - they'll evaluate how his asperger's is pregressing/improving, how his vision and attention are, how his motor skills and balance are developing - the whole she-bang.

~amy