So just to clarify...
Old 160GB classic = Wolfson Dac
New 160GB classic = Cirrus Dac (same as iPhone 3GS)
Is that accurate?
There is a post here claiming that they tore down the Classic and it had the Wolfson DAC, but every other source I have seen claims that the current Touch, iPhone 3GS and 160GB Classic (Sept 2009 refresh : 6th Gen, Rev 2) all use the Cirrus DAC. I maintain that there is more to it than that, and the Apple engineers have done some tweaking, and Wolfson would still be supplying DACs for the Nano (I think the current Shuffle has the Cirrus DAC, but I havent seen that in black and white). All I know is that the current Classic sounds better than any iPod I've ever heard - you need to hear it for yourself.