I own a DF4, and while it's a great bike, mine took some fiddling to get it working. The seat post binder is an issue, you may have read about it. I have a PVC pipe down my seat the as insurance against slipping (and it was slipping at first). The latest seat post clamp has an insane torque rating thatI'd be afraid to apply to a bolt that size. I don't, and it combination with the PVC pipe, it's no longer moving. Also, I had some headset issues, now fixed. I'm really happy with it now, but it took some work to get it solid. The aero seat post is not even something I was looking for, but the price was too good to ignore.
From those I know who have the Dixie, the 56 is pretty short. Most people who would usually be on a 56 are on the 58 Dixie I believe. You should go by the reach figure in the geo chart rather than the top tube length with that bike.