iPod Touch 4G + Line Out? (And iPod Touch vs Zune HD)

So you might have remembered my thread asking about good portable players. It was suggested that I get a Clip + and as much as I like the idea of a cheap high capacity player, I do appreciate the iPod Touch's UI and functionality. 

I have quite a few questions. If you can answer just one, I'd be thrilled. Sorry to be a nuisance.  

1.) Does anyone know of a way to get line out on a Zune HD without a dock or powered device?

2.) How does the sound quality compare between the Zune HD and the iPod Touch 4G?

3.) Is it still possible to get line out from the iPod Touch 4G?

4.) Can you get line out from older Zunes such as the 80GB or 120GB hard drive based ones? And their sound quality?

5.) What are your opinions on using an amp directly with an amped headphone jack vs. line out? Does it make much of a difference?

Thanks a bundle. Again, please don't feel like you have to answer them all. However, if all of the answers are found, I can compile them so that other people can find out for them selves. I am sure I am not the only one.

Thanks.

Again, please don't be scared off by the amount of questions. A lot of them are out of curiosity and not really necessary.