This should do the trick:
SELECT Name,
SUM(Quantity) AS SumQuantity,
SUM(Volume) AS SumVolume
FROM (
SELECT CASE WHEN SUM(Volume) OVER() * .03 < Volume THEN Name ELSE 'Others' END AS Name,
Quantity,
Volume
FROM #RESULT
) AS data
GROUP BY Name
ORDER BY SumVolume DESC
-- Gianluca Sartori