There are some very interesting and surprising results here.
First, it's one thing to make a silent video card, but when that video card surpasses a card with active fan cooling by double-digits, that is pretty noteworthy. And that is what the Gigabyte 7600 GT Silent-Pipe II did compared to the reference 7600 GT in the 3d Aurora case: the Gigabyte 7600 GT Silent-Pipe II was 12 degrees cooler than the fan-cooled reference 7600 GT under load. That is very efficient cooling, and surprising as I expected the silent card to be a little hotter than the reference board under load.
It's also interesting to see how Gigabyte's card performs in different case scenarios.In the Sunbeam Samurai case with the side fan off, the Gigabyte's silent card is very close to the reference card in thermal performance. I hypothesize that this might be because the Silent-Pipe II relies on convection to pull air in the second slot it uses, while the open grille on the side of the case lowers this pressure. It also provides air from another direction, preventing it from flowing ideally around the card and to the case fans above.
In the same case with the side fan activated, performance improves a lot. This fan provides sufficient airflow to cool the Silent-Pipe II, even though it is not in the optimal direction.
The best-case scenario in our tests was the Gigabyte 3d Aurora case. Without a disruption in airflow from side fans, the card worked ideally as designed and convection pulled air in past the card to the case fans. Even with the fewest fans and quietest case, the 3d Aurora allowed for a marked improvement in cooling over an actively-cooled 7600 GT reference card.