I have nearly the same question but I shoot events, concerts, conferences, sports (indoor cheerleading), landscapes, candids, award ceremonies and lots of group photos. So I really do appreciate having a lens that can handle lower light conditions as needed.
What I currently own, 70-200MM 2.8 OS Sigma (non Macro), 17-55 MM 2.8 Canon, Sigma 8-16MM Ultra Wide, and Canon 28-135MM kit lens. Obviously using the kit lens less and less now that I own the Canon 17-55MM. and 1.4 extender on a 7D.
Here is a few on my radar:
30MM Sigma 1.4 or 28MM Canon 1.8
10MM Sigma 2.8 Fisheye
135MM Canon f/2
Sigma 150-500MM (for outdoor widlife)
I plan on spending 2 to 3k on lenses in the next 6 months. With the addition of a few more lenses I'll likely permanently retire the 28-135MM but I must say its been a great versatile lens. Very happy now with the 17-55 2.8 and the 70-200 2.8 so a 24-105 f/4 would be both overlapping and also a loss of an f/stop. I appreciate being able to shoot in lower lighting conditions.
Any suggestions here? Happy with Sigma and Canon quality. I have no first hand experience with Tokina.