I am so angry with myself. I jsut wrote a super long response to your post but now I have lost it. And I am out of time to rewrite an answer. But let me just say this.
Please consider that, with your son's characteristics, you may be dealing with a gifted child. Gifted kids are often misdiagnosed as ADHD or Asperger's because they look very similar. Most teacher's have no idea what gifted looks like but they gone to seminar after seminar of what ADHD or HFA looks like. In fact, quite a few psychologists can't tell the difference because they haven't been trained to.
We are going through something very similar to you with our 5 year old and we have been told by all sorts of people, teachers, SLP's even one psyc that our son may be asperger's or HFA. But none of them want to address the fact that he is extremely intelligent (math at a second grade level, perfect pitch, able to replicate 10 measures or so of classical music when given the chance to focus on a piece that he really likes). We are having him eval'd at the school district and fianlly, someone sees it! The school psyc has said he wonders if his behavior in preschool is due to boredom and wandering off mentally to think about things like math or music.
PM me if you want to talk. I just hate that I lost everything I just wrote for you.
Check these out and educate yourself before jumping into the realm of ADHD, Asperger's diagnoses with an extremely intelligent child.
http://www.nagc.org/index.aspx?id=986
http://giftedkids.about.com/od/giftedandld/a/gt_and_ld_3.htm
http://www.hoagiesgifted.org/