The cultured No.15 has played 114 times for Edinburgh, scoring 20 tries, and in that time has become a regular member of the Scotland squad.
Long-kicking Southwell was given a huge vote of confidence at the start of the 2009 RBS 6 Nations by former coach Frank Hadden when he was named at full-back ahead of Chris Paterson.
But although he played with composure in a Scotland side lacking direction and success, he had to make way for Scotland's record points scorer against Ireland.
The 28-year-old then endured a damaging conclusion to the championship when he was concussed as a substitute in the Calcutta Cup match, only returning to action last weekend.
Now Southwell is poised to widen his career with a stint in France - and has heard good things about life in Paris from Taylor, who made the same move three years ago.
"I spoke about Paris with Simon during the Six Nations and he told me good things about the club and the city," revealed Southwell.
"I've had a great time at Edinburgh and have made some really good friends but when the chance came to play for Stade and I felt it was right for me."