I currently own the 50A, 35A, and 24-70 II. Honestly, I am reaching for the 24-70 II far more than the others. The issue gets to be that the thin DoF of less than f/2.8 is great for those special shots, but also limiting for everyday shots. I had to learn this after trying to shoot f1.4 to f/2 for a couple of events and missing a lot of shots.

Another way to put this, if I had to limit myself to two lenses on the 5DIII, it would be the 70-200 II and 24-70 II.

Where I find myself using the 50A is when I don't use a flash and indoor low light events, or when I want the very shallow DoF. Then, I just shoot a lot so I have a couple of keepers.

For what it is worth, the 24-105 is a great lens. I had been tempted to go with it and primes. It's a great value in a kit or purchased used. Another option would be to get it and a prime.

Good luck.