I'd like to relate my experience with the Classic. . . but go easy on me, I'm new and ignorant here.
This is only the second iPod for me. I got a silver 80 GB Classic intended as a replacement for my old 1st gen iPod, which incidentally is still running on its original battery.
Isn't it amazing how these things have improved? The Classic is half as thick, plays well over twice as long per charge, and holds 16 times as much on its hard drive. However. . . I do prefer the old scroll wheel that actually turns. Sometimes the touch-wheel doesn't respond immediately. I've also noticed the little delays and sluggishness in the Classic's interface, though it's not too bad.
After using the Classic for a couple of days, I found myself feeling oddly dissatisfied with it, but it took a while to pin down exactly why. It just didn't sound as good with my ER6i earbuds. It sounded weak somehow. The bass seemed particularly weak. I set the EQ to "bass booster" which made it sound a bit less weak, but soft and muddy.
I rooted around in my closet and found a small battery-powered amplifier, which is called a "Pocket Amplifier 1". I've had it for several years, but never found much use for it until now. When I put it between the Classic and the ER6i, the music came to life! It sounded strong and clear -- pretty much the way it had always sounded with my 1st gen iPod.
The only conclusion I could reach is that the amplifier circuit in the Classic is considerably weaker than the one in the 1st gen iPod. The old iPod had enough "juice" to drive the ER6i pretty well, but the Classic needs help.
Have Apple been making the amplifier a little weaker in each successive iPod generation, hoping we wouldn't notice?
I finally dug out the earbuds that Apple packed with the Classic. They sound surprisingly good, considering what they are. They may be cheap, but at least they were well matched to the device they were bundled with.
I'm still thinking about where I go from here. Turns out the old iPod with the ER6i was a pretty good combo, and maybe I didn't appreciate what I had. The Classic + PA1 + ER6i sounds great, but the PA1 itself is as big as my old iPod, so it sort of negates the advantage of getting a slimmer iPod. Even after I velcro them together, it's still a bit awkward.