Plugging modem wall warts into power conditioner?

For the high end, try Acopian.

For cheaper ones, and sometimes some very good deals, eBay is one place. Another might be a local electronics supply house. For example, in Montreal there is Addison.

Please list some sources for linear power supplies ? For Mac Mini?

Agree with Rbautista about substituting a linear power supply of the same rating for the wall wart. Doing that improved sound from two DACs I own ( Muse TDA 1543 and Apogee Mini-DAC ).

My experience is not quite the same but thought I would share since I view my SB Touch as "mini-computer".

When I first got my SB Touch which used a switching type wall wart, I plugged it to my Richard Gray thinking that all recommendations of using a linear power supply would be mute since the RG conditioner would "clean" things out. In my setup, it did not. I would still her intermittent clicking from the wall wart.

In my setup I also use a wireless bridge that I have my SB Touch connected to. I haven't tried this yet, but SoundCheck from the SB forums recommends replacing the switching wall wart with a linear supply also. In his findings, it makes a difference. So in your question, it could make a difference, but maybe replacing the cheap wall warts might have a bigger impact first and the conditioner will probably just refine it more. Just my guess.

Switching-type wall warts inject noise back into the AC line. A small isolation transformer will block this and in addition give the wall wart cleaner power to switch. It seems to work for me.