Fan noise can be reduced in quite a few ways. Most obvious is RPM, slower fans make less noise, many come with speed controllers so you can set the speed based upon the cooling you need to achieve. Some fans including some Zalman quiet fans cheat in my opinion by simply fitting a resistor in line which reduces the speed of the fan.
There are other technologies that help reduce noise. For reduced noise choosing the right bearings can have a big impact, particularly as fans age they tend to make more noise. One of the best rated options out there are the SSO-Bearing's developed (?) by Noctua, which in prolonged testing retain a lower dBa output than typical ball and sleeve bearings. Also some manufacturers have developed fins that maximise airflow while reducing turbulence and so have a lower noise output per CFM. Also never forget the mounting options, if you simply use metal screws against a metal case fan socket you are much more likely to get more vibrations and so more noise, if you use soft rubber grommets that will greatly reduce vibrations and so noise, most good quality fans come with rubber fittings includes now.
As for increased CFM, there are options out there, i already mentioned the blade shape which can impact both noise and CFM per dBa. In addition some more 'exotic' developments are available, for example the Zalman Sharkfin design is supposed to reduce turbulence even more and so reduces noise per CFM. Then there's the Sharkoon range that use dimples like you see in golf balls to enhance CFM per dBa.
Basically there are lots of options, but the important points are RPM used to achieve the CFM you want. dBa output per CFM to find a fan with the lowest noise for the CFM you need. Bearing type to minimise noise, especially over the life time of the fan. Then how you fit the fans to the case to avoid vibrations.