I'm not sure if I ever replied to this thread over the year it has been here but I have mentioned this before in other threads and I have used multiple types of fans from various companies including the big names.
The Panasonic Whisperquiet fans are without doubt the BEST overall for stealth. I did a comparison test way back when I did my tent write up. These fans are awesome if you are worried about noise. I use a 6" in my closet and I sleep 10 feet away and can't hear it.
I saw a few threads about the endurance and strength of the fan. All for the bad side, but I went ahead and ordered one just to see for myself. I hooked it up in my attic back in April of '08 and have not turned it off since. So this proves the endurance. It keeps my tent 2 degrees above ambient cooling a 600 watt. So it has strength in distances under 10 feet.
I will agree that any run longer than 10 feet may have a problem tho. That's where the other fans are better. But you pay for that type of strength with a ton of noise.
The 8" would probably do a 15 foot run with a few turns in it. There are a few places to grab the specs on these before you order.
http://www.ntsupply.com/files/products/FV-40NLF1_Spec.pdf
This shows the drop off once you get passed the 1.0 static pressure mark. But who cares? You still get 200 cfm at 1 sp and it will be so quiet you can stand next to it and whisper to a friend. If you add insulated duct you would be able to make a baby sleep right next to it. No shit.