Accessing my Cox digital phone line from my Desktop a'la VOIP (e.g., Google Voice)

Greetings,

(unfortunately, I may already know the answer to my question, based on failed forum searches, and a Chat conversation with Cox tech support...  but I'll ask, just in case)

I currently use Google Voice to make and receive calls from a software interface running in my web browser.  I have a regular headset connected to the audio jacks on my PC, and this solution is seamless with other uses of the headset.

Feature-wise, this is a great solution for my needs.  In practice, however, I have a couple of problems that I am tired of dealing with (latency/lag, and complaints from my co-workers that when I am connected to a conference call via this interface, there is unacceptable background noise).

I would like to have the same capability from my Cox digital phone service.  In other words, I want an interface from my desktop (browser-based, or otherwise) that will allow me to make and receive calls over my Cox service.

Does that interface exist?

Thanks.

- s.west