One example: I recall when Star Wars came out, a lot of my friends bought the soundtrack. It served as sort of a gateway to classical music. It's hard to measure, of course, but I'd bet that that had a larger positive impact on classical attendance than, say, Hannibal Lector killing people to Bach's Goldberg Variations had a negative one.
To your lack of visual stimuli hypothesis, I'd also add as other more likely drivers of classical's decline:
a) Live classical music is expensive and getting more so.
b) Sound quality in a concert hall is different than via digital means. It doesn't wash over you like it does when listening via your Bose headphones. It's less visceral and more distant. And you have to tune out the other sounds of coughing, people shifting in their seats, etc...
c) And finally, we have the best recordings of any work available on demand. In economic terms, that creates really cheap substitutes. Speaking for myself, I'd rather just listen to the Vienna Philharmonic on the couch for free than dress up, drive across town, find parking, and pay $100+ to hear the Austin Symphony play the same work.