You indicated that the psychologist suggested there is an auditory processing issue (probably because of the lower number in digit span) and that you didn't know how to follow up. I heard Linda Silverman speak earlier this month. My notes indicate she refers people to the Able Kids Foundation In Fort Collins, CO for Central Auditory Processing disorders. http://www.ablekidsfoundation.org/
You may want to check their website to get more information on CAPD and see if it seems to fit your kid.