I am getting a 40D next week with the 28-135 lens kit. After spending hours on various forums my short range plan would be to spend some time getting to know the camera and then to sell the lens kit since they seem fetch around $300 and apply it towards a Canon 17-55 2.8 IS and the 70-200 f/4L IS with a 1.4x extender. Any suggestions for the gap? This is kind of maxing my lens budget so don't suggest another L lens to fill the gap. How critical is this gap? Thanks.