Thanks for all the replies! The 17-55 IS is a serious possibility right now, and I'll definitely be getting the 70-200.
I think you guys are right, with my current glass lineup, I'm always finding something missing but haven't been able to put my finger on it.
60d + 15-85 + 50 f1.4 + 70-200 instead
He has the 7D, but the lens suggestions are good. I would definitely prefer a 35 or a 28 to a 50 on crop. The 50, first the 1.8, then the 1.4 was my first prime with a DSLR. When I got the 28 and the 85 I found I didn't use the 50 anymore, so I sold it. I eventually replaced the 28 with the 35L, which is my favorite lens.