Well... Just to help you along...
I think if you got a 10" scope, you probably wouldn't use your 8" much. The 10" is just as easy to move around (I think) but wil show you a lot more visually.
So you could always sell your 8" to fund the ED80.
With the 10" on the EQ6 you will still need a guide scope either way.
I envy your position, I'd be happy with either setup
Good Luck!