well,
I think SQ of all older ipods is pretty crap but the G6 sounds pretty decent. I can easily enjoy the sound of the G6 and the Touch out of the headphone out.
The GUI is very simple, so that's good, but at the same time lacks some handy features. Things aren't always there where you'd expect them to be, like shuffle for example.
Overall I'm very happy with the classic but the clickwheel isn't very responsive, it's quirkly and sluggish. I'm not new to clickwheels, but the old ones were much better.
BTW, I just posted my rigs a few posts ago. The source in my rigs, especially in the small rig, is not always the same. It can differ.
With these:

You see (top left to bottom right):
Sony PCDP D-E401, Sony PSP Slimline, Sony NW-E407, Sony NW-A1200, Sony MZ-RH1, Sharp MD-MT180H, Sony NW-S703, Sony NW-A805, iPod touch, iPod classic.
Greetz