I run the stock 16" wheels in the winter and 17" after market wheels in the summer and although there isn't a great deal of difference it is noticeable. The short wheelbase doesn't help the ride either. Nothing you can do about that. Probably the biggest factor is what you're point of reference is, i.e. your previous/other vehicle. If your coming from a Lexus/Buick/Lincoln, or any full size sedan/SUV for that matter, the xB will not fare well by comparison. My other vehicle is a 14 year old truck, so the the xB's ride seems fine even with the summer wheel setup. Rather than tweak the xB, get your husband an old beater truck. He'll quickly learn to appreciate the xB.
Other than that, tires/wheel size are about your only other cost effective option. I have a friend who replaced the 16" wheels on a Honda Element with 15" wheels and a taller profile tire to maintain the same overall diameter. I think that would make for a softer ride, but might make the handling a little squirrely in emergency situation. My friend was happy with the result on his Element, but then again his name was Odd Larry.