I would agree with polarbear.
You've already had a psychoed in the past year, so you're probably better off going straight to a neuropsych, as, if you see an ed psych now, s/he will have to either use the old cognitive testing information, or switch to an alternate instrument to collect data directly. If an alternate instrument is used, and then you choose to pursue a neuropsych, there may not be any good cognitive instruments left for the neuro to use, since he'll likely have had the good ones already in the previous 24 months. (And if he hasn't had the stronger ones, that probably means the ed psych gave a less informative instrument, which is also undesirable.)
On another note, I should point out that you already have documentation that he is 2e: he's identified gifted, and health impaired. And it's a health impairment with known cognitive effects. If you're in or moving to a public school (actually many privates, too), it might be advisable to start at least the 504 accommodation plan process now, as you have clear documentation of a disability with significant possible impacts on educational access (not only instructionally, but in the larger school community).
