Quote Originally Posted by Sean Setters View Post
To me, the Canon EF 24-70mm f/2.8 L USM II makes the most sense. It's an excellent general purpose zoom - and that seems to be where your current kit is lacking. The EF 70-200mm f/4 L USM is a fantastic lens, but there are many times when you need a good zoom lens below that focal range.

The 24-70 should come in very handy during weddings, especially with a full-frame body that handles noise as well as the 6D does. While primes are fantastic for weddings, they can be problematic if you aren't carrying two separate bodies on your person at all times. Wedding moments are so fleeting that it pays to have a single lens that can cover a wide range of situations without having to change lenses.

But jrw is right - figuring out what you want to do but are currently unable to do with the gear you own is the best way to determine exactly what you need. :-)
That is kind of what I have been thinking. When I used the 60D the 17-40mm was my go to, now with the 6D its a little wide. The 24-70mm on the 6D would cover that same range as the 17-40mm on the 60D and more.