Matt, the Sigma is a good lens, a little soft at f2.8 but stopping down a little and it's great. Focus is fast too plus 1/4 the cost of the Canon 24-70L
The 17-40L is an awesome lens, wish I have the money. You didn't order it at Dell did you? They have the sale last week.
The 28-135 fit your range but I'm sure once you put on the 17-40L you won't go to this lens anymore
. Also check out the Tamron 24-135mm.
I'm thinking of the 70-200 F4 next... need second job
Some pic of the Sigma