the top card would be hotter, but not by much and not to the point where it chokes either. This blower thing your on about won't offer any temp decrease, it will actually offer worse airflow and worse heat dissipation. Hot air rises, so the top card is always going to get hotter as the hot air is going up, no other setup or configuration can have such a huge impact on temperatures. The ACX cooler has a much better cooler, with the fans pushing air up, where it is supposed to on the PCB, the cooler is much more effective and will keep the card cooler due to the cooler design, as it is designed for better heat dissipation then the stock cooler.