That first book is really the only one, IIRC, where the Delgado scholars play a large role.
I've already got all of the audiobooks, so I can't take advantage of that discounted Whispersync offer, though I think I did pick up most of the audiobooks via various sales at Audible.
I think that the only one I actually paid full retail price for was the CD version of "Local Custom" narrated by Michael Shanks, which is available through Buzzy Media. That was the only Liaden Universe book available in audiobook format for the longest time, until Audible finally began to issue them.
(And I even bought the Audible version of that one, too. 
)