Marco: believe me, I was just as surprised as you are! I went in to the dealer ready to love and buy the SR17s. I heard the SR17s, and the dealer said 'wait one sec'. He put the SR15s up, same room, electronics, etc, and they really were markedly better in every area. The SR17s just sounded a little muddy in comparison.
This is really subjective, and I'm sure others disagree. Just my opinion.
Also, you're absolutely right to be mentioning production cycles. Alan Yun changes things in significant ways, and sometimes it's impossible to tell what's what unless you ask him.