You might consider to use state-of-the-art hardware instead of outdated stuff. Newer systems can be more energy-efficient.
One thing is that a more energy-efficient system can often be run fanless. This not only reduces the noise level, but also increases reliability.
Another thing is energy cost - at least for users who don't have an electricty flatrate. The break-even point for newer, mor expensive hardware with energy consumption is typically after two years, compared to "some old junk" which is few years old and you can get for free.
I keep the "old junk" with it's noise fans around as backup systems, in case the shiny new modern systems fail.
Another point of caution: I have experienced that many switches are unreliable. For example, I have several D-Link gigabit switches lying around which will occasionally just "hang" - network traffic doesn't get through any more and the switch has to be power-cycled. I have found that I can reproduce this phenomen simply by pushing 100MBit/s of traffic shrough the switch; it will "hang" after a few minutes. That sucks. What good is a 1000MBit switch which cannot cope with traffic of 10% link capacity?
I currently use Cisco gigabit switches. They seem more reliable. Not "Linksys by Cisco"; I've experienced issues with some of these as well!