Elite Bastards posted a review on the ASUS EN8600GTS Silent video card

Atop the GPU core, and also covering the board's memory, is a hefty heatsink, which draws heat away from the GPU via two heat pipes. This is coupled with a third heat pipe , which is linked to an even larger heatsink positioned away from the graphics board. This takes its cue from the EN7900GT TOP part we mentioned earlier, as this larger heatsink can be rotated through ninety degrees to pull it away from the graphics card itself - This should then sit above the CPU cooler, so that the air pushed up from that cooler helps to cool this heatsink, and thus the graphics card itself. Of course, this will cause a problem for users of certain third-party CPU coolers, which either take up the space that this cooler would occupy, or remove hot air elsewhere. Users looking to build an entirely passively cooled system may also struggle, as without some form of active cooling to help dissipate heat from that heatsink temperatures can rise unacceptably very quickly. Thus, you are left wi th some trade-offs and points to consider if you're interested in picking up a silent graphics board of this performance level.

ASUS EN8600GTS Silent Video Card Review