You find the Mac Mini to be acoustically noisy, Adam? I sure as heck can't hear mine, even nearfield.
Neither can I. In fact, it is one of the reasons why Mac Minis are so popular among audiophiles.
As for whether upgrading the power supply is worth it, I don't know, but too many people have reported good results to not give it some consideration. In my experience, any potential upgrade to the power network, whether it be power cords, power supplies, or even wall outlets, results in improved sound IF you select the right equipment.
Bernard,
You might know about and have already done some of these, but as far as getting better sound from a Mac Mini is concerned, I would rank the following improvements I have experience with as such:
1) More memory. Going from 2gb to 8gb RAM will blow you away;
2) A high quality (notice I did not say expensive) USB converter, even if your DAC has a USB input. I probably should have put this #1. Getting a good one is like getting a new DAC.
3) Isolate, both in terms of physically away from the DAC and vibration control-RFI/EMI management. Synergistic Research makes some expensive isolation platforms that some Mac Mini users love, but you don't have to spend that kind of money to improve in this area. Core Audio's platform has been well received;
4) Solid state hard drive. Not as much impact as upgrading RAM, but definitely worth it.
5) I upgraded the power cord on my Mac Mini with excellent results.
If you are not already aware of it, computeraudiophile.com is a great resource for all of this. Sometimes the discussion can get bogged down into the hyper-technical (at least from my perspective), but there is more than enough great information to make it worthwhile. This guy went nuts in upgrading his Mini:
http://www.computeraudiophile.com/f...e-pocket-server-music-server-step-step-17666/. A much less involved upgrade process is discussed in this thread:
http://www.computeraudiophile.com/f10-music-servers/macmini-how-best-spend-buck-17024/.