I'd say, step back and look at the big picture of what you need, telephony-wise, rather than getting lost in the nit-level configuration details. Then, you can easily configure things accordingly. For example, how many inbound telephone numbers do you need, and how many different destinations do you want those inbound calls to ring to? For example, do you want to give out your two different GV numbers and/or a CC number, and have them all ring to one phone port, with your cordless phone plugged in? Or, do you only need one or two of those inbound numbers?
After deciding that, then we can come up with the simplest and most reliable solution.
You mentioned that you like Callcentric's features, including its voicemail. Google Voice is not designed to simply be a free telephone line; its own voicemail system is integral to the service and cannot be disabled. So, if you want to standardize on CC VM, then that's an important factor in designing your configuration. If you attempt to forward GV to CC, but configure it to grab the voicemail messages, it's possible that some messages may still end up on GV's VM, depending on your configuration. In that scenario, you'd only use GV for outbound calls (since, for example, calls to most US and Canadian numbers are free), and use CC for inbound.
On the other hand, if you are just using GV for fun/experimenting/spare lines, then you can just leave those GV accounts separate from your CC number.
I give out one Google Voice phone number to my contacts. That one number forwards to a CC DID, configured on multiple OBi and other VoIP products, via CC extensions. Unanswered calls go to GV VM. I also have a couple of other CC DIDs that used to be my POTS home phone number and office number, and those ring to the same destination phones, via CC "Call Treatment" rules. I can call outbound with any of those numbers as caller ID.
