My BayBus arrived today. I decided to order a BayBus from PCmods instead of building my own. After thinking about it for a bit, I realized that each DPDT switch cost 5 bucks and the BayBus cost 20 bucks with four switches. I save no money doing it myself and I get a much higher quality device by purchasing theirs. I guess I’ll be working on my fans today.
For prosperity, here is a diagram of the three position 12v-off-7v trick to undervolt fans for lower noise (and throughput, of course):
This is akin to the 7 volt fan modification from overclockers.com. but it uses a three position switch to control it at two speeds.