I strongly recommend the Sigma 17-50 f/2.8 OS DC EX HSM. $594 at B&H right now »
www.bhphotovideo.com/c/p ··· _DC.htmlAnd then if you're really wanting a fast prime for low light, shallow depth of field work, check out either the
Sigma 30mm f/1.4 $489 or the
Canon 28mm f/1.8 $484