your wic cards for cisco's are generally for WAN...ie. T1 which is pinned differently than cat5 standard (568A or 568B)...WAN interface for WIC dsu/csu is pinned 1,2,4,5 (rj48c)..your ethernet port is pinned 1,2,3,6..therefore, from the cable modem "out" (rj45) to cisco "in" is ethernet..so two ethernet would appear to be your answer..the other type of wic would be serial v.35, but that has no place in your situation....also, if you try to manipulate a ethernet input into a WIC card, dont forget that dsu/csu (rj45) cards would need a timeslot statement for the number of 56/64kbps channels from WAN....
i am not a cisco expert(ccna, ccnp), but i do load their configs and install them for a service provider... my experience is on the T1 and Fractional T1 to WIC......
hope i have helped and not been confusing