All modern aftermarket coolers do the great job when cooling GPU, but they dissipate heat inside case, and I think that's a major flaw. Once, there was a dozen od DHE (Direct Heat Exhaust) coolers available, but not anymore. DIY PC users solve this with a Borg-looking installations, with a bunch of additional fans and so on - not something you want to do to a beautiful and very silent Mac Pro.

I have found some PCI cards with fans - but they are not suitable for a Mac install beacuse they need a free Molex connector (not very elegant to pull one out of optical bay) and they bl°Ck one slot - and in HR-03 case that is "one slot too much" as this monster cooler with a fan attached uses ALL slot space available.
Then I found this: A Pack of 4 Vented Expansion PCI Slot Covers for Improving Rear Case Airflow ($7.99)

Very simple and cheap solution that provides "70% venting percentage". Looks too trivial, but at $7.99 it was a no-brainer and worth a try. (FYI - The MDD and G5 towers I had came with perforated (holes) PCI slot covers.-Mike) To my big surprise, even such a simple modification, made a significant improvement in air-flow. Now the expansion bay temperature was up only by 2°C, and temperature of the hard disks also went up no more than 2°C. Good start!

The other improvement I have made is the way how the fan is connected. At my first attempt I used temporary connection from other source and the fan ran at constant speed in non-PWM mode. I have done it that way beacuse I didn't want to cannibalize the original connector - and I had no luck in finding another one. So, if it's on low revs, it's silent, but the whole thing can overheat in a Mac Pro with 4 drives. If it's on high-revs, we have done nothing - noise again. Maybe, not as noisy as the Stock one, but you can hear it. So, the solution is to use a modern PWM fan and to connect it that way - so that firmware on the graphics card can control it. It's delicate to solder it and the wires are color-coded differently!

NVIDIA <---------------> Arctic Cooling
mini-PWM connector <-> standard PWM connector
black = black (ground)
yellow = red (12 V)
green = yellow (sense)
blue = blue (control)

Once you do it, the thing works like a charm - virtually silent most of time and it spins up if temperature goes out of control.

Now, I have done new set of tests (Room temperature 31 °C, without AC.)

NVIDIA 8800GT Stock cooler (in °C)
• Hard drive bays: 39, 37, 38, 38
• Hard disks: 48, 48, 48, 49
• Expansion slots: 44
• GPU core, GPU memory, GPU ambient (idle): 70, 54, 58
• GPU core, GPU memory, GPU ambient (stress): 85, 77, 79

Thermalright HR-03 Plus + Arctic Cooling 92 mm PWM fan + Silverstone Aero Slots
• Hard drive bays: 40, 38, 39, 40
• Hard disks: 49, 48, 49, 50
• Expansion slots: 46
• GPU core, GPU memory, GPU ambient (idle): 61, 53, 57
• GPU core, GPU memory, GPU ambient (stress): 75, 67, 69

So, now this seems as an improvement. I'll continue to test it. But even now, when it seems that it works acceptably I still would not recommend this cooler for Mac Pro owners.

Pros:
• very, very quiet
• cools GPU efficiently (probably the best on the market)
  (FYI - the Accelero S1 Rev 2 cooler also got good comments, suprisingly even if fanless. And is lower profile.-Mike)
• good build quality
• cool 6-pipes-monster-look.
  
  Cons:
• takes up ALL available slots!
• extremely troublesome installation (screws too high for a Mac Pro, delicate connector soldering)
• needs quality additional 92 mm PWM fan and Aero Slots covers
• dissipated heat inside case and raises exp bay and hard disk temperatures
• expensive all around

I hope it's of some help to fellow Mac Pro users!
Best, Davor Pasaric

P.S. - And some fresh photos...

Photos

Other Video Card Cooler Articles (incl. 8800GT): - see the Coolers section of the Video Topics page.

If you've done a Mac graphics card cooler swap/mod, install guide, etc. let me know the details. Thanks.

Other Graphics Card and Video Articles: - See the Video topics page.