Canon 6D and 50 1.4

I own a Canon 5d Mark III with the 24-105 and the 50mm f1.4. I used the 50mm a lot in a 40D but now that I moved to full frame I find it a little short. I am now looking to buy an 85mm and a 135mm prime. You will most certainly love primes and the small DOF on full frame. I don't agree with others that prefer the Sigma. I find Canon 50mm f1/4 to be better. But of course it's a matter of taste, technique and luck. My 50mm was not always in focus with the 40D but with the 5D is much better. I tried different Sigma and Tamron lenses and always ended up returning them.

My piece of advice is wait a little. Fing out wich focal length you prefer with the 24-105 ( it might be 24mm if you shoot landscape most, 50 mm for street photography or 85-100 for portraits) and only after that buy a prime with that focal length. Whatever the focal length you wil choose to start with, I am sure you will love primes and will buy more