Hmm. Are those screws or rivets?

You could remove the PSU and drill/grind them out. Just be careful around the capacitors, and don't put it down on anything conductive.

One _very_ good reason _not_ to run with the cover off is to prevent somebody from reaching in the closet and electrocuting themselves. It would also increase the risk of something getting into it (like fleece lint) and getting ignited somehow.

I really would be tempted to get different fans for it and see what the effect is. Those switches were built for heavy duty use - I bet that if you looked at the specs that they would be quite happy at elevated ambient temperatures, and that is the reason for the loud fans. (Ever been in a server room when the AC fails?!) I'd bet that they'd run quite happily with quiet fans.

Questions; What is the power rating on the back of the switch? What is the rating of the fans?