I think our buddies are mostly correct here. The high-end Swiftech kit doesn't cool any better than a CNPS-9500LED or the ThermalRight Ultra-120. At least if you use thermal resistance as a comparison measure.
Here's what I did, and it's worth between 2C and 5C degrees of improvement:
Cheap As Free -- mobo ducting -- John Cinnamon
Note especially that he's reporting that his ducted system still shows 9C degrees above the CPU temperature for watercooling. But he's not using a top-end heatpipe cooler in the comparison. And by that comparison, the stock retail cooler without ducting runs about 35C hotter than the watercooled system.
I had a 3.0C Northwood OC'd with DDR500 modules to "DDR480" in this ducted system, and the highest load temperatures with 75F room ambients never went over 43C or 110F. We put the same mobo, processor and memories in a midtower box for my brother's Xmas gift, using the same XP-120 cooler and an attempt to provide plenty of case-ventilation -- but no ducting. At load, his CPU temperature is about 5 to 6C higher, and his mobo temperature is significantly higher with the same room ambient.
A 2'x3' piece of foam-art-board costs about $6 at Michael's ARts and Crafts -- the tube of glue is about $2. A 1' x 3' piece of 1/8"-thick lexan is more like $10-something, and you need to buy a bottle of Poly-Zap glue.
The same case and ducting for my system currently cool a Prescott 3.4Ghz OC'd about 10%, and running at full-load with a room ambient of 75F degrees -- the CPU temperature seldom climbs above 40 to 41C. I had replaced the XP-120 (thermal resistance = 0.15) with an SI-120 (TR somewhere between 0.11 or 0.13 -- and forget what Citarella reports at OverClockers. He's using conservative estimates for comparison purposes, and the unit is still among the best.)