The Stormers supplanted the Bulls at the top of the Super Rugby table after week 13 of the competition while the Brumbies, Crusaders and Sharks stayed in the hunt for the playoffs.
The Stormers beat the Waratahs 19-13 in Cape Town to further dent the Australian side's top-six playoff ambitions.
The Stormers lead the standings on points difference from the Waikato Chiefs, who had a bye this weekend, while the Bulls are two points back after going down 16-11 to the Highlanders in Dunedin.
The Brumbies tightened their grip on the Australian Conference with a 37-25 win over the Hurricanes in Wellington.
The Crusaders crushed the woeful Auckland Blues 59-12 to keep in touch with the Chiefs in the New Zealand Conference.
The Sharks are sixth overall after downing the Cheetahs 34-20 in Bloemfontein.
Wallaby fly-half Quade Cooper played his first rugby of the season as defending champions Queensland Reds posted a bonus-point 34-20 victory over the Lions in Brisbane.
IN yesterday's game, the Melbourne Rebels beat the Western Force 32-31 in Perth to leapfrog the Waratahs into third spot in the Australian Conference.
Meanwhile: DHL Western Province were crowned Vodacom Cup champions for the first time ever when they beat GWK Griquas in a nail-biting final at GWK Park in Kimberley on Friday evening.
The Capetonians' victory by 20-18 - sealed by a converted try by flanker Rohan Kitshoff in injury time - saw the Vodacom Cup travel south of Bloemfontein for the first time in its 15 year history.
