Upload & Sell: On
I made the step from 5DII to 6D in June. The 6D is better.
How much hassle is too much hassle is entirely up to you. For me, it's normal. Part of my lifestyle. Buy stuff, sell stuff.
I sold my 5DII for about half of the cost of my 6D. I'm good with that. If you can break even or better, (which I think is true) then what are you waiting for?