This is what I was concerned about... traditional telephony and voip are two hugely technical subjects, both describing what to the layman is the same thing (telephone calls), but in reality are two wholly different technical areas.
The problem is compounded by the fact that there are people who will sell you a "voip service"... that service can be anything from a single "telephone number", and which you need a voip phone (hardware or software, to a complete full blow IP PBX.
Heck, even the concept of a "phone" (handset) is now wholly ambiguous. To most people, a phone is the thing they pickup. In voip, a phone can be that. It can be a dedicated IP phone (c/w with ethernet port and no PSTN port), it can be a USB attached phone, which still needs some software to work. Or it can be software (think skype) running with a mic and speakers.
In days past, customers only had to be capable of plugging a handset into a wall socket. This was the demarc point. All the complicated technical equipment was hidden behind the demarc (exchanges, modulators, pbx, switched, ESS, SS7, System X, etc), and was the responsibility of the telco. And with the exception of PBXs, that was the same regardless of your supplier, be it BT, AT&T, BellSouth, RBOC, etc.
Voip changes that. Your supplier can be responsible for as little or as much of the technical part as they choose.
When I said "its possible", what you are trying to achieve is possible.... the way you described it wouldn't work. Which way you go about doing it depends on what voip system/service you have/choose... or may be dictated by the requirement to add the Miggy into the mix.
Voip is actually straightforwards and "easy"... once a few basic principles are understood, so don't let me dissuade anyone!
Asterisk is a wholly free software PBX, runs on Linux. "Which flavour of linux..." any. But there is a simple, straightforward solution: have a gander at
http://nerdvittles.com/Home of what was "Asterisk@home", trixBox, and now in the latest incarnation, PBX-In-A-Flash. Complete solution on a single ISO distro, based on Centos. D/l, burn to CD, stick in machine (with internet connection) and power on. One reboot and a few key presses later, a complete IP PBX in your own home.
regards the Phonepak, it may be irrelevant as there is now a bid on my item and I cannot end the auction. If you win, we can progress. Or, I'm quite happy to provide input assisting via another route, e.g. any fax-capable modem attached to a soft-pbx via an FXO card.
Regards the POTS (Plain Old Telephone System, ie legacy telephone devices) ports on SOHO routers, I've only very limited experience of a Draytek (and that was when I was doing some WDS work for two farmers with a single dsl line provided via a wireless link). The Netgear is considerably cheaper - in the UK - than the Draytek, and
almost as reliable. Whether they work with fax is another matter, I don't know what service they can carry on the POTS port other than voice, or whether it is a full FXO port.
Brgds
Alan