i'm looking for a lens to use for studio portraits, i shoot w/ a canon xti. currently i use a cheap canon 35-80mm lens and it's ok, but i want something better and sharper out of the camera. i'd also like something i can use to walk around with, for everyday shots. i like my 50mm 1.8, it's nice and sharp, but i want something with range.

i've been looking at the canon 17-85 is or the 28-135 is.

any thoughts?

looking for opinions on either lens or to really make things confusing, any other suggestions? i'd like to stay under $300 & am trying to find either one of these lenses used.

thanks,
liz