jax2- the only reason i said what i said is because your initial reply indicated that the poster "needed" to do certain things. IMO, there are much better alternatives to what you stated. let me clarify: etc...
I believe I've already responded by explaining my initial post. My experience with the AE and Squeezebox have been far less than stellar, and certainly would not lead me to wanting to use either in any kind of critical listening. For a system you listen to while doing other things they'd be just fine, IMHO, YMMV.
I completely agree, that the SlimDevices remote interface is not very good, especially in comparison to iTunes.
As far as other wireless solutions; the reason I recommend and use an Airport Base Station is the setup interface is easy and intuitive. It does not require multiple calls to someone in a call center in India with a script. The reason I did not recommend using an alternative internal wireless card for the poster's G5 tower is because the issues around signal transmission have something to do with the all-aluminum body of that computer as I understand it. There are some aftermarket companies making antennas for it, and hopefully Mac has addressed the issue by now. I have a g5 2.7 dual-processor model and a working AirPort card and their rare stock antenna. That setup is utterly worthless and will not transmit a signal 20 feet. I don't know if a different internal card would make any difference, and again, you'd be losing Apple's intuitive and simple interface in setup (the same interface you've praised for their iTunes remote abilities).
The Slimdevices Transporter uses a AKM AK4396 multi-bit delta-sigma DAC. AKM DACs are used in the Gryphon Mikado and the Esoteric D-05.
Again, AFAIK the only source of digital streaming from an AE is optical (toslink). The other connections do not stream digital signals. That is unless the design has changed substantially from the two units I own. Have you used a coax cable into a DAC with an AE?