SELL THE DARN 17-40
I don't think much of the 17-40L as a lens for a 1.6x camera. It may be an O.K. wide angle lens for a full frame camera but, the focal range is more like a mid-range zoom for a crop camera.
As a mid-range zoom it falls short in that:
The f/4 aperture without image stabilization is just too slow. I much prefer a minimum f/2.8 aperture for a non IS lens.
The long side of this lens is too short. An equivalent 64mm is pretty lukewarm and a vast difference from the equivalent 80 or 88mm of lenses with a 50mm or 55mm long side.
IMO, the 12-24mm Tokina f/4 would be a great match for your 28-75mm lens.