another recommendation on the axiom streamliner rack that has the setback that gains a few inches. Given how much you plan to carry, they are well made and would be fine, using lighter weight panniers will help also.
I put a streamliner on my wifes bike a few years back and its a perfectly good solid aluminum rack, not pricey at all as a bonus, and specifically designed for road bikes without eyelets for racks (hence the skewer mount system)