If you're pretty sure it's SPD, it would be an OT. Beware that many (most?) school OTs either (a) don't officially recognize SPD, (2) aren't experienced/trained enough in SPD to know what they are talking about, or (3) even if they did, they may not be permitted to treat it on a global level, which can involve an OT gym and be rather expensive. Usually school OTs focus on things like handwriting ability, and the whole IEP process is involved. We've done OT for SPD privately and were relatively pleased with the results. I've also spoken with one school OT who won't even discuss SPD, and another one who seemed well-versed and had plenty of home recommendations but was not allowed to treat anything except for my ds's fine motor (handwriting) situation.
I think that there is also quite a bit of variability of expertise in SPD amongst private OTs as well.
If you're not sure you're looking at SPD, I'd consider seeing a neuropsych for issue-spotting purposes. (Isn't what the Eides do a neuropsych eval? You could find someone to do that locally though that can be expensive too, as you know)
I'd also take a look at some books on SPD to consider what type(s) of SPD you are dealing with, e.g. Miller's "Sensational Kids":
sensory modulation (sensory over-responsivity, sensory under-responsivity, sensory seeking
sensory-based motor disorder (dyspraxia; postural disorder)
sensory discrimination disorder
that's my two cents. now off to fiddle with my internet connection...
I do not believe that any doctors (psych, neurologist, etc.) are involved in "diagnosis". I don't think it's necessarily possible to officially diagnose SPD until it's included in the DSM or some such thing, which last I heard it was not (though I do not know the status of the DSM V)
Some websites that may or may not be helpful:
http://www.starcenter.us/sensory-processing-disorder.htmlhttp://www.spdfoundation.net/
