PowerColor uses Vortex II cooling on its PCS+ HD 7970 card and it has no trouble cooling the factory overclocked Tahiti XT chip.
Before we move on, we must note that we changed the thermal paste because two screws were quite loose and the paste hardened a bit. We noticed about 4°C lower temperatures after replacing the thermal paste with Gelid’s GC Extreme.
All in all, Vortex II does its job well and remains quiet throughout. In fact, we were quite surprised with how quiet it is because we couldn’t hear the fans, not even after long gaming sessions. Temperatures climbed up to 80°C, which is fine considering the GPU clocks and silent operation.
After our additional overclock to 1175MHz, temperatures rose by 5-6°C, but the fans were still quiet. 
As you can see on the pictures below, Vortex II enables the fans to be elevated by 1cm compared to its initial position. You can incline them or leave them perpendicular, so there’s room to find optimum settings in your case. We tested the HD 7970 Vortex II in Corsair’s Cosmos II case that boasts excellent airflow, so inclining or elevating the fans didn’t do much to provide better cooling. Namely, we measured a single °C of difference. 
