I'm not in North America, so I don't know much about Callcentric. If you can have free incoming calls on Callcentric on sp2, then you can still use:
Voice Services > SP2 Service > X_InboundCallRoute:
{ph,sp1(12222222222),sp1(13333333333)}
You can use two OBi110s on the same network. In fact, that is my setup here. I would recommend changing the UserAgentPort to be unique for each spX if you do that. If you do not need the Line Port, then an OBi100 is a few $ less. Another option, if you do not need any Line Ports, is to replace your OBi110 with an OBI202 which has 4 spX.