Thanks, all. I just successfully registered an outbound account with circlenet.us
(taking advantage of their $2 credit offer) and will, as of May 15th, switch to circlenet for outgoing calls and will continue to rely on my free callcentric did for incoming calls (using GV number forwarded to callcentric). I prefer the pay-as-you-go approach, especially given circlenet's extremely inexpensive prices (I never make international calls, and my outbounds probably don't amount to more than 300 min. per month).
The callcentric number has served me well for over a year now for inbounds without dropped calls. I migrated to an Obi202 from a Linksys PAP2T - GV - sipgate - SipSorcery combination for many years (got a bit weary of programming dial plans in ruby, though!).