The change actually came with the 2012 models. So the quotes above are almost correct, but the changes to the original 2009-2011 system came with the 2012 models, not the 2015 models. In short, the 2015 models had the same stereo as 2012,2013, and 2014. The 2011 was the last year of the slightly better sounding, but less reliable sound system.
If unsure, go back through the old Lexicon sound system threads comparing the 2011 model to the 2012 refresh (I had bought a 2012 new myself).
If unsure, go back through the old Lexicon sound system threads comparing the 2011 model to the 2012 refresh (I had bought a 2012 new myself).