bluefront is the man to ask about PWM fan noise...
the doors by the filters only affect backpressure, and i don't think they would have much of an effect on cooling, but noise may have been reduced ever so slightly.
my case has a mesh front, so even tiny sounds come right out and bug me, like the seeking of my 160gb IDE drive...in a well soundproofed car, it would sound like wet brakes.
what you may try doing, is ducting the ninja to the exhaust fan, scrapping the idea of a CPU fan, and just run the whole rig with two fans, keeping the drives (my idea remains the same) at the bottom, cooled by the power supply.
i was only curious about the ninja, most people here have it bolt thru, only because of its weight (my reason for getting a rev. A).
Its widely accepted that if you have two identical fans running at the same speed, its just the sound of one fan, +3dB. this is correct because every 3dB a sound becomes twice as loud. so, say you go with a Scythe Slipstream, guessing, the 800RPM model. according to www.scytheusa.com
the 800rpm model is 10.70 dBA at 12v. so, if you run two at 12v, it will in turn be approx. ~14dBA. now, generally, its hard to hear anything under 16dBA until you're in a dead quiet environment where everything seems louder than it is. so say you decide you wont run the fans at 12v, you'll be adventurous and go down to 7v. If you run the fans off a molex or 3 pin connector, at 7v, you're looking at <14dBA...hell of a silent rig there. go for PWM, and you'll have clicking to deal with.
stash the drives at the bottom with the power supple, two fans in the "upper chamber", one blowing on the 8500gs, the other being exhaust, ducted to the ninja.
you could also go for 3 fans, and stick a fan down by the power supply at hard drives, and use a fanmate on all of three of them (not unheard of), but the fans, well, if you use a zalman fanmate, you have a choice of fan, Nexus, Yate Loon, S-Flex, Slipstream...or you could just try to undervolt the Slipstream. running one PWM however, will give you clicking sound, but that's bluefronts' department, i don't have a slipstream [in fact i was thinking about those new Noctua fans for my rig].
http://www.silentpcreview.com/forums/vi ... hp?t=45788
^thats plenty of good reading material on the subject, from the master himself.
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