the only 8800GT ive seen with passive cooling included, is the Sparkle version... when i checked a few days ago it wasnt yet available, but maybe thats changed since.
what oswold said is right though... ocing isnt really an option, but as long as you dont mind that, and are primarily concerned with how audible things are, then itll work fine.
im not aware of the thermal limits of the 8800 series, could be above 100C even (the thermal limits of the 7 series for example was as high as 115C on 110nm process), but either way i would imagine they could easily handle a passive cooling solution, also because of the much smaller 65nm manufacturing process which helps keep temperatures more acceptable too... and if it cant be kept stable on passive cooling alone, itll most likely say on the box or manual or even their site i would imagine ('needs sufficient additional cooling, etc', which also kinda negates the reason for passive cooling to begin with, which is primarily silence, if only)