"Tamron SP AF 28-75mm f2.8 XR DI MACRO (B&H USD$319) OR Tokina 28-70mm f/2.8 ATX Pro-SV (B&H USD$279)"
The reviews I've seen indicate a bit better optical quality in the Tamron. Both are extending barrel designs.
The Sigma 70-200 f2.8 is superb, and sharp even at f2.8. I got mine from KEH. Suggest you check their web site a few times a week.
Joe
