I took a second look at PDAudio, and the maker of the Live2496 software verified that three PDA models are good for 24bit 96kHz taping (and a few more good for 24/48).
http://live2496.com/phpBB/viewtopic.php?t=136The bottleneck is still the cost/availability of the PDAudio CF card, which makes this kind of rig "not great" value for money.
I also realized that all Macbooks as well as Powerbook G4 Aluminium came with optical inputs:
http://guides.macrumors.com/MacBookThe older models (released around 2005) can be had for $230 and upwards on Ebay, which makes them a good deal and qualifies them on the list above, although hardly for stealth.
You could also go 24bit coax in by popping a VXpocket or EMU 1616 Cardbus into most old laptops. Take a look at used Fujitsu tablets (to keep down the size) with Cardbus slots, they run Windows proper and can be had for less than $100.
The going rate for the soundcards are $130 and upwards on ebay, so total budget might even be cheaper than the Macbook, but of course more fiddly (breakout cables, drivers).
I've updated the list above...