Hi guys Im fairly new to the world of photography but have had plenty of fun with my Canon EOS 450D and the following two lenses: Canon 50mm/f1.4 Canon 70-300mm f4-5.6 IS USM Only problem is that im not able to go below 50mm and I have thus begun searching for a more 'normal' everyday kind of lense. The requirements are that it should be fairly lightsensitive as I will often be using it for concerts in dark rooms. Also im thinking somewhere in the range of 17-70mm-ish but I am fairly open to ideas as long as it is able to reach somewhere in the vicinity of 17mm. Also my budget is somewhat limited. I have been looking at the Sigma 17-70mm/f2.8 lense and wanted to check my alternatives. Thanks in advance!