Quote Originally Posted by photosurfer
i would like to take the plunge into L glass

FWIW, Sometimes the non-L glass has higher image quality.


Quote Originally Posted by photosurfer
i'm looking at picking up a used canon 28-70 f2.8 L

Your 17-50 f/2.8 is sharper than the 28-70 L (and even the much more expensive 24-70 L). It would be a fine choice if you are willing to live with lower image quality.


Quote Originally Posted by photosurfer
i like the 17-50 range but i would like a little more reach on the long end,

The 17-50 is a 3X zoom. The only way to get "more reach on the long end" without giving up wide angle is to go to a superzoom like the 18-135, 18-200, or 15-85. Of those, only the 15-85 provides excellent image quality. If you're willing to sacrifice f-number to get more zoom range, it may be a good choice.


Instead, I suggest you go with a telephoto lens.


Quote Originally Posted by photosurfer


and . . .the other option would be a 70-200 f4 non IS, as i've heard a lot of good things about it. Any thoughts?

It's a good choice for the money, if you can't afford the 70-200 f/4 L IS. Another consideration in that price range is the Sigma 50-150 f/2.8. There have been some quality control issues (Sigma ships more "bad" lenses than Canon L), but the "Mark II" version of this lens has improved a lot, and when you stop it down to f/4, it's even sharper than the 70-200 f/4 non-IS. It would really help to have the microadjust feature on your camera body.