Tom -
Is this going to be a surprise for her birthday? Are you willing to give her a card with a promise of a new road bike instead of having the bike to hand to her? (OK, your post does say you're going to shop together, and that's good.)The reason I ask is that fit is so important - if you have a decent bike shop they should be able to set your wife up to test ride several different bikes. At this point I am riding bikes that were custom-built for me - but when I was riding "regular" bikes I found that a test ride really helped me to identify the best bike for me.
--- Denise