i found this wicked website which has some pretty in depth analysis of consumer and pro audio cards.... analyses things like frequency response, noise level, dynamic range, THD, IMD and stereo crosstalk.
here's a little example:
on the left, Soundblaster Audigy Platinum EX, on the right, ESI Waveterminal 192X (my card )
TOTAL HARMONIC DISTORTION:
interesting stuff eh
here's the website: http://audio.rightmark.org