If the problem is mostly that the tires on your Dolce are too skinny, why not just get another set of wheels and mount fatter commuter tires? Should be a heck of a lot cheaper than a whole 'nother bike.

That being said, I bought a 'cross frameset (LeMond Poprad) & built it up for commuting. I didn't want a slow bike with a long wheelbase, but something that was snappy like my road bike, but that had mounts for a rack & that I would put more gears on vs. my regular road bike.