As stated I would talk to the installation supervisor at Comcast, but both the DSAM and the 860 are capable of doing the required home certifications if Comcast has the proper server. If they have the required server, I would go with the 860. Little less on price, less hassle if upgrades are required, and they have a DOCSIS 3 modem already in production.
This is CABL.com posting #293328. Tiny Link: cabl.co/mbotg