First of all, what is the point of comparing 5 or more heatsinks, every one with its own fan, rotating at different speed? Even if all fans were set to rotate at the same speed, it still wouldn't have been a fair comparison, since - obviously - different fans move quiet a different amount of air at same RPM. Having the NV120 with a fan @ 2700RPM outperform the Ultra 120 with a fan @1900RPM by 2 degrees doesn't tell anything about the cooling efficiency of those heatsinks. Using a reference fan would be more difficult, but would render more comparable results.
Secondly, sound pressure measurements of a cooler in a case with 5 fans simply doesn't sound convincing to me. The 80mm fan of the power supply would be enough to mask the majority of noise generated by the different coolers - are you sure you need a 1000W beast for testing CPU coolers? Overclocked CPUs tend to be power hungry, but a far more quiet PSU would do a perfect job.
Furthermore, a 33 dB (A) is far too high noise floor to reveal any meaningful details about any cooler; it may allow the noise character of a cooler to be perceived (or measured) only when it is set to rotate at high RPM, which is an area where most heatsinks tend to behave more or less equally. Low RPM measurements are far more revealing for the quality of a heatsink design, I think.
And one more point: acoustic measurements presented that way are very much useless, they simply confirm what everyone around knows quite well: lower RPM means lower noise. After all, it is the fans that are being tested, and here we come to the first argument I pointed out (the heatsinks introduce some turbulence noise, of course, but given the similar design of modern CPU coolers I tend to believe that it isn't as important as fan quality itself).
I hope that some of my remarks were useful to you - the only point for me to provide them is to ensure that you publish even better reviews in the future, not that I'm a fan of a certain brand. :)