The guy at the Trek shop did say that while I looked more comfortable on the 56, he thought it might be because I'm used to being stretched out.

The seat tube angles on each are different (73.7 and 73.4 for the Treks, 74 for the Dolce and 73.5 for the Giant), and if I remember correctly, I think the stock stem on the Dolce is shorter than the stock stem on my Avail, so that may have something to do with it. If anyone's got a link explaining geometry as it relates to fit, that would be awesome. I'm interested in learning more about frame geometry as a whole, and I think that's a good practical starting point.

As I said, I'm in no position to buy just yet, and they'd probably take a little more care with the fit when I show up and am serious about buying. I'll see what's available in the area with regard to fitters (thanks for the tip, Indy!).