OK. Here's a few things I found out.
ASIO by pass USBAUDIO.sys. that's what it's desing to do.
I think M-Audio is not designed to work directly with USBAUDIO.sys.
On the other hand, Benchmark DAC1 is design as plug & play with some sort of fimrware to use the native driver, USBAUDIO.sys.
by the way, Anybody know if ASIO4ALL pass through DD/DTS?