if you want a lens with large opening, get any of these: 16-35 2.8 (70k+), 17-55 2.8 (50k+), 70-200 2.8(60k+), 24-70 2.8(60-70k), or 50mm 1.8 (4k+, pretty cheap)...
I suggested 17-40 4L (30k+), coz i thought you were in a budget... sorry... hehehe...
well, the 17-40 4L, actually performs well. This is what we use in shooting whole body portraits and macro like shooting.. food, products, etc... it can't give you the same bokeh as the 17-55 2.8 though.
if you want great bokeh when shooting portraits, get the 50mm 1.8 or 70-200 2.8 (i just love this lens, i kinda forgot that i have a 50mm 1.8 because of this)
