5DIII. It'll give you better high ISO performance for dim areas, and make all the lenses more useful for "normal" photography.
If you're open to the idea, you could consider a 5DII and the 24L or 35L, which would give you 24 or 35, 50, 85 and 70-200. With primes at 24 or 35, 50 and your 70-200 zoom, might not need the 24-70. You could also get an 1.4x extender further along the road if you don't shoot near 300 that much.