remember one thing though, CFM and dBA numbers measured differently from company to company. In some part, you hafta go reputation as well. I mean, look at SilenX fans. There is no physical way you can convince me the numbers they rate their fans at are accurate. I'm not saying they aren't dead silent, but their CFM ratings are often way too high to be reasonable.
I agree, Vantec products aren't as quiet as they claim to be. They are pretty quiet undoubtedly, but to a super quiet freak, they're just average. Seeing as how their products generally don't cost very much, the old saying goes, you get what you pay for.
Nexus fans are very nice. I can also vouche for the Arctic Cooling 80mm Pro TC. TC means Thermally controlled and it is very quiet. Doesn't make any unncessary noises (ie. clicking, whining, motors), only the blowing of air. great fan.