Yeah I think you're right, JohnK, check out
http://www.audioholics.com/techtips/specsformats/upsamplingvsoversampling1.php
It has a nice description of oversampling using electrical engineering lingo.
If oversampling isn't built in on the standard commodity DAC then the $30 players don't have it (an addition $0.10 part on a player that costs a couple bucks to manufacture won't make the cut). Judging from the NRC anechoic chamber measurements that Ian's been publishing for various Axioms, there's a dip in the high teen kHz in the tweeter frequency response, but there's still response at 20kHz, so if there is >22.05kHz digital crap it'll be played by the Axioms. Maybe some receivers have the ability to filter this stuff out too.
--Martin
