|You are going to have to make some changes at home before you'll be able to make the VoIP phone work.|
You metion having a 2wire device. This will be a "combo" unit that is a modem/router/wireless AP all wrapped up in one device. If I'm correct, you'll only ever be able to daisychain your second router to the 2wire.
I've never played with VoIP at home so I know nothing about that side of it (but I know all about the Enterprise side of VoIP because we use it at work) but if wanderer is right, then your VoIP probably still won't work even if you have it plugged into the 2wire with a network cable.
From the sounds of it, the router you got from your company needs to be the unit connected directly to the internet.
If this is true, you need to get a modem that is nothing else but a modem. Then you would plug your company supplied router into it.
Since you're using ADSL, I suspect you have phone outlets all over your house. There's nothing stopping you from plugging your ADSL modem in upstairs where you need the VoIP phone. Then, plug your company supplied router into it. You could then bridge the 2wire device to that router and set it up downstairs and connect your PC down there to it.
This solves all your problems but is dependent on you getting a modem from your ISP that isn't a combo unit. Some ISP's, like mine, supply that equipment. Other's charge the customer for it. With luck, your ISP is like mine. If not, you might be able to claim it as an expense at work and have your company pay for it since it will be required to make the VoIP phone work.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.