well i did a lot of research in the past few hours and decided to get the Tamron 17-50mm f/2.8. I had a hard time choosing between the Canon 17-40 f/4 and the Tamron 17-50mm but decided to go with the Tamron which is much cheaper and is a f/2.8 and i dicided save up the rest for later on. I might get the 50D body soon so its better if i get the Tamron and save the rest for the new body.