DACs: Airport Express vs waveterminal vs mini-dac


I know this is impossible to quantify, but with a good stereo system (Cayin TA30 tube integrated amp & Green Mountain Audio Europa speakers), what's the magnitude of difference using the following dacs?

Airport Express (I already have the AX, and can connect it to the integrated amp with RCA's [analog])

Waveterminal U24: computer to USB to waveterminal to amp (waveterminal does the DA conversion)

Inexpensive DAC like ART DIO with waveterminal: computer to USB to waveterminal to ART DIO to amp (ART DIO does DA conversion)

Apogee mini-dac: computer to USB to mini-dac to amp

Other?

What's the best bang for the buck?
mschamberlin3865
96kHz is only available on the newer Macs.

I think that the newer Macs have the Crystal CS84xx which is actually the same chip used in a lot of high end DACs.
I have compared using Airport Express and hooked it up to my Meitner DCC2. All files were Apple Lossless. And yes, the Meitner CDSD-DCC2 is still heads and shoulders above Apple-Airpot Express-DCC2. Not even close.

Having said that I love using playlists for "background listening" such as parties. dinners or when I am working on something so it does have its purposes. The question I have is there a major audio quality difference btwn the wirless solutions....somehow I doubt it...Airport, Sonateer's Bard Audio etc...I am sure Wavelength etc will be better than the wireless solutions but then it simply doesn't work for me as my files are in PC and external hard drive in a different room. My thinking is that if I want to really up the ante on sound quality while retaining the functionality, then either need another notebook + wavelength....or go get a sep hard disk based player such as those offered by Olive and then hook up to the DCC2 and use the latter's DAC.
I have a headroom total bithead right now, which goes out of the USB of any computer (instantly recognized as a destination for sound out in your preferences) and to some ultimate ears or powered monitors. it's more than okay and a huge improvement over the minijack out for the cans. however, I am looking into the apogee mini-dac, and the wavelength brick, for a more permanent setup with a computer that I might leave in my main system. another thing I tried is the new outlaw rr2150 receiver, which is a strong integrated amp that has a USB input. sounds pretty great for the money