I tried this as a little project over the weekend. Since the arrl had a ssb contest over the weekend.
I used the mixing board that my band and I use when we practice at my house called mackie mixer but the behringer mixer in the example in youtube video below works just fine. I hooked the mackie mixer with my icom 706.
I found if nothing else being able to clean up audio on the receive was a great tool and gave me an edge in contest since I was able to clean up audio and get contacts that for months I have been struggling to get. Cleaning up my audio on the send was help as well I got great audio reports the entire contest.
Its hard to say if sending was better cause I can not here myself on the other end I was however getting 599 from contesters. The receive is definitely worth it I was able to take far away sounding, crackley, echoy and distorted voices and clean them up and make them clear to be able to hear better to make the contact.
You can do this with almost any cheap mixer and a few adapter cables its worth the time and the few dollars. Even if your just going to use it for receive.
Our friend Bob Heil has an example of how to do this on youtube