If money is your concern, buy used headphones. Worst case that you don't like it. Sell it back with a small loss + shipping. I have 10 headphones right now, 8 of them are used, never had any problems with them. r/AVexchange is wonderful for this. Just do your due research, look at seller's reputation, posts history, check sold prices of similar items in recent months, etc...

I bought my HD800s used with all original accessories minus the box. No issue at all.

Since I don't have HD560s, I am not qualified to compare them with HD800s. However, I do own HD600, and HD6XX, I think I can give general answer to your questions:

• Are the HD800s better than the HD5** and HD6**? YES
• Are they $700 - $800 better? NO
• Will you ever touch your HD560s again if you bought the HD800s? YES, you should.

- I would like to elaborate this further: in my limited experience, the deeper I am into this hobby, the more I appreciate the differences in my headphones, I like to change them according to mood or music genres. It's always fun to discover something new in a song when you go back and forth on different set of headphones. Maybe one day I will finally find a perfect headphones that make me sell the rest of my collection, but HD800s ain't it.

• Are the HD800s worth the money? Only you can answer this question.

Hope this helps, happy hunting.