I know nothing about Macs but the SBT plays 24/96 files and 24/192 files (downsampled to 24/96) from my PC wirelessly.
As Kal points out, it will go to 24/96 via wireless, but NOT via iTunes. You will need to put your hi-rez music in a separate folder. In the Squeezeserver "Settings" window, choose the iTunes tab and check "use iTunes". Doing this will cause Squeezeserver to catalogue your entire iTunes library. Then go to the "basic settings" tab and go to the line that defines "music folder" - here is where you will tell Squeezeserver that other folder with your hi-rez music. It can deal with both iTunes and one additional folder in this way. I'm just assuming because you are on a Mac that you are actually using iTunes. If not, obviously you only have to deal with indicating where your music folder is.
So when the touch gets a 192 file it ALWAYS downsamples to 96? I just downloaded my first 192 file from HDtracks, and it plays and sounds good, but since I didn't have anything to compare with I wondered if it was in full 192 or 96. Is there any way to get it to play 192 files or is 96 the max?
Yes, I'm using iTunes. I've been able to get it to take both 96 and the 192 file, and display it as such in iTunes. But I'm wondering if, given that it displays as 96 or 192 in iTunes, it is being transmitted to the Touch in high rez. I don't have a separate hi rez folder, just a "music folder" that holds all my files -- and they list the resolution 44, 96, or 192, in the iTunes library. Jax2's comments makes me wonder if I need to do something else, or if I've stumble onto setting it up right without really knowing what I was doing.
The Touch, itself, cannot handle a 192kHz file at all. It is the SqueezeServer on the PC or Mac that will downsample the file to a format acceptable to the player. It will downsample to lower bitrates for other SB players.
However, if you try to play a 192 file on a USB drive connected directly to the SBT, it will fail and not play at all.