Windows iTunes- AX- Toslink- DAC Bit-Perfect?

Hello all,

I recently read that Windows Base System (iTunes) to Airport Express (with digital output) may not be able to by-pass the k-mixer in the windows.
If this is true, how is the digital signal get alter in the k-mixer? (Upconverted to 48k then down convert to 44.1k?)
Is Windows based iTunes -> AX via mini toslink -> DAC Bit Perfect? What if the remote volume is disabled?

My understanding is that Airport Express is in fact the ONLY way to get bit perfect output from iTunes on a PC (Macs allow bit perfect output via other ways). I've read posts where people have tested it and confirmed it's bit perfect.

I use a (Red Wine Audio) modified M-Audio transit as a source from iTunes with the "remote volume disabled" and it sounds fantastic. Not sure what it does or does not bypass, but I hear the computer's other beeps and such through my headphones, which I actually don't mind because I'm using my computer while listening (for me, it's a nice feature).