There is a popular website that advertsies on many forums including here and e-bay. This group is called "Biblical Unitarians" I believe that they are associated with "Christian Educational Services"
I believe that there are several problems with the beliefs of this group.
Not only do they deny that Jesus existed as God before he was born to Mary, but they deny that he existed at all in any form before being born to Mary. Even the Watchtower admits that Jesus pre-existed his being born to mary (though they believe that He was an angel.)
The following is from the site:
"There is no question that Jesus figuratively ?existed? in Abraham?s time . However, he did not actually physically exist as a person; rather he ?existed? in the mind of God as God?s plan for the redemption of man ."