I've got a 7.4FX myself and since switching the 28mm tires I have seen a nice increase in speed. I have actually ridden a metric century with the 7.4 and was able to ride with a group of roadies and keep up an 18.5 mph pace (I even did my share of pulling).
All that being said I have gone to a true road bike for longer rides. You might consider a bike such as the Domane which, while it has curved handlebars, has a more relaxed geometry and is very comfortable. You can even add brake levers to handlebars if your wife does not want to ride on the hoods or in the drop position.