canon 15-85 vs tamron 17-50 (non VC)

[ogrec]

i currently own 15-85, its good daytime outdoor general purpose lens, but its max aperture is really low and i find myself taking canon 50mm f/1.4 at night (when i cant use a tripod) or when i want to take photos of people (or other subject requiring better dof)
i've been comparing resolution charts here at TDP and i dont see such a huge difference between 15-85 and tamron. distortion, ca and vignetting i dont consider a problem cause it can all be fixed in post so image quality, maximum aperture and flare resistance are most important to me

i'm considering selling 15-85m and buying 17-50 tamron and put the rest of the money into savings for some prime (maybe 100mm f/2.8 macro or 10mm f/2.8 sigma fisheye)
theres also possibility of selling 50mm f/1.4 which i find myself using about 10% of the time, but the thing is i really like it as a portrait lense and if i sold it and bought 17-50 tamron i'm afraid i'd spend most of my time using tamron and 15-85 would sit at home so it would turn out a bad decision...

buying canon 17-55mm f/2.8 is not an option, its currenty out of my price range
my dslr is canon 60d

pleas share your thoughts

edit: i just remembered something thats probably important, i'm mostly using 15-85 i 15-50mm range, so tamron would fit there, except that its widest angle is 17mm... i'm not certain how big of a deal that is