Kit Canon Rebel

Kit Canon Rebel
What is the best all-in-one lens for a Canon Digital Rebel?

I'm looking to upgrade from my kit lens on my Canon Digital Rebel XT. I can spend about $ 500. I want something like the Sigma 18-125 in terms of scope, but I've heard mixed reviews about it. I have done much research now that I am confused. Any suggestions would be great!

Canon EF-S 18-135mm f/3.5-5.6 IS lens http://www.bhphotovideo.com/c/product/647015-USA/Canon_3558B002_EF_S_18_135mm_f_3_5_5_6_IS.html Sigma 18-250mm f / 3.5-6.3 DC OS HSM Autofocus Zoom Lens for Canon Cameras If you're confused http://www.bhphotovideo.com/c/product/609113-REG/Sigma_880_101_18_250mm_f_3_5_.html now believe that many different opinions will make it less confusing? That's why we never ask for opinions when I'm making a purchase. I do my own research and make my own choice. You'll hear mixed reviews on just about everything.

Canon Rebel XTI (400D) Kit Unbox/ The Costco Kit