The model no. for SP AF17-50mm F/2.8 XR Di II VC LD Aspherical [IF] should be B005. B003 is for AF18-270mm F/3.5-6.3 Di II VC Macro. Both B005 and B003 are under promotion (upto Oct 31) - $200 coupon.
I'm considering B005 for Nikon. The price is about $3850 (same for Canon mount). "Shing Shing" offers 5 years warranty while other shops usually offer 3 years warranty only.