If the big consideration is really sound, doing whatever is necessary to use larger, but slower (wide, high CFM per dB/RPM) and higher quality (fluid dynamic bearings) fans might serve the purpose regardless of other hardware. Some of them are rated to be <20dB, quieter than a whisper, and fluid bearings are supposed to be mostly impervious to the noise added by aging that hits a lot of fans.

I know, but you were thinking it SO LOUD.