I see your in Cambridge, go to Wheel Works in Belmont on Trapelo Road. They've got a good selection and a lot in stock. Don't go on a weekend though. Their sales people seem pretty decent. CycleWorks in Burlington is good but their stuff tends to be high end and expensive. I'd avoid REI or EMS, they tend to focus more on Mountain bikes and dont have that wide of a selection.
I just got my wife a Trek 7300 for like $435. WSD bikes are usually a little shorter from seat to handlebars to accomodate their shorter torsos. And the cross bar is lower to make it eaiser to get on and off.