For voice, the 202 should work quite well. Each GV number could ring to one or both of the phone ports. You can also use different ring patterns to know which number is being called. Outgoing, each port would have a default account; you would dial a prefix to select an alternate. It's also possible to set it up so calls to specific numbers would use a designated GV account.
I agree with Ostracus on Callcentric for incoming fax. They support T.38, so you could also reliably send from your fax machine via the OBi ($0.0198/min.) (The OBi is limited to four registrations, so one of your GV numbers would have to ring in e.g. via a free Callcentric number, and any outbound calls showing that caller ID would have to be made via CC or another paid service.) However, for most uses, an web-to-fax or email-to-fax service is easier. What kinds of documents do you fax? Approximate usage?