Looks more like you want a subquery, not a temp table.

Something like:

SELECT U.actionID,
   M.CardNum,
   M.serieID,
...
FROM  Upgrades U
   LEFT JOIN Media M ON U.serieID = M.serieID
   INNER JOIN (SELECT U.OldCardNum,
          M.SerieID,
          M.SerieName
       FROM  Upgrades U
          INNER JOIN Media M ON U.OldCardNum = M.CardsBegin
       ) sub ON sub.SerieID = M.SerieID;
Where...